Grow Mediums HELP! D39. My 5th growth in row is failing. (1st with autopots) Yellowing TOP leaves. PH, zinc,iron, something else?

[Trichome Jim]

I don't think its a matter of not enough aeration, I had a issue similar to this due to the feed being too low and messing with the ratios needed to balance my plants needs during transition. I took it off the autovalve and flushed it with .8ec ph'd to 5.8 with enough that i was confident i completely flushed the media then top fed for a couple days raising the ec upto 1.3 over that time before going back on the aquavalve. Seems to have worked for me, stopped the symptoms and the plant recovered. Some people will say not to flush autopots but at that low of a feed you will not have any buildup of salts which is why they say not to do it.
Here is a before and after of the issue I had

 

[Cannaficionado]

Im no expert but I would think an immobile nute deficiency or lockout as its yellowing on the top. I cant tell ya which. But man o green will get you pointed in the right direction

 

[BipolarBear91]

@Mañ'O'Green - here is my attempt to provide the best info I can. I will be using CAPS LOCK/bold for the information that seems most relevant to me By the way thanks for asking to take pictures in daylight, the symtoms dont look as bad as in the tent.

This is my water report – I translated it from my native language. It doesn’t include calcium and magnesium…. But it has AMONIUM and “chlorides”. Do you think my water has chloramine or chlorine?


Aluminium: 0.02mg/l
Amonium: 0.03 mg/L
Boron:0.4mg/L
Iron: 0.08mgL
Fluorides: 0.17mg/L
Chlorides (plural?): 75mg/L
Manganese - 0.02mlL
Natrium: 34mg/L
Nitrate(s):1.9mg/L
Nitrit (s) 0.003mg/L
Oxidizing ability(?) KMn04 – 2.3mg/L
PH: 7.3
Sulfates: 41mg/L
Copper: 0.05mg/L



I will use Hannah scale for Ec measurements. And answer to your question is "yes -tap water is 300 ppm aka 0.6EC.

Problem: Yellowing/chlorosis(?) from TOP leaves starting day 35. Up to day 35 everything was almost perfect. (SMALL nute burn starting day 24, but so small it didnt get worse))
-Medium/grow method: 100%CANNA (pre buffered) coco coir in 15 litre plastic pot. Watering is done by gravity aka "Autopot" system - it bottom feeds and refills the tray, when plants drinks everything..
-Feed and supplements used: Sorry, wont be able to provide NPK, but I used Canna Coco light feeding chart and went even lower than their recommendations. However I reduced the feed evenly for all nutes, as to avoid relatively disproportionate amounts.

Autopot system is meant to start bottom watering when plant is big enough, roughly 15-25 days. ALL MY PPMs are including the RO + tap+ calmag base.700 ppm means a 200ppm base of RO/tap/calmag and 500 ppm of nutes.

Day 0 - day23 = handwatering to 20-30% runoff. Ph about 6, ppm 500-600. Runoff EC good.
Day 23 - day30: Autopot turned on. 12 litres of 650 ppm water, 5.65 PH. SLIGHT NUTE BURN. I mean barely visible burned tips on leaves
Day 30 - day37: 15 litres, 700 ppm, 5.65PH. Didnt increase PPM due to last weeks nute burn. Nut the burn was so small I didnt want to lower it.
day 37 - today: I lowered the PPM to 600 AND the PH to 5.55. My guess was iron,zinc def and I read that lowering ph can help iron/zinc absorption. Has it gotten better? No, but I also cannot tell how much worse it has gotten, not too much.

-Water source: 80% RO/20% tap = 50ppm or 0.1 ec. I add Canna calmag to reach 0.4ec and then I add Canna nutes (A+B, Cannzym, Rhizotonic). Water PH is reservoir 5.6-5.9 (it drifts to 5.9 in 3-4days) Water PH in tray (bottom feed) = 5.7-6.1. PH OF WATER HAS NEVER BEN ABOVE 6.1
-Strain and age: Mephisto S.O.D.K - day 40
-Climate: 24/0 light, so climate is consistent. Temps 25-26 celsium (maybe a bit LOW for leds) and humidity 60-70%. Ambient temps around 23 celsium and ~60-65% humidity. Due to , in my opinion, insufficient leaf temps with led lights, the VPD may not be ideal, but it is nowhere close "bad"
- Light used: Kingbrite 240wwith cree red and Mars ts1000. Distance varies,I go more by DLI. DLI is about 37 now. That is for my lights 24-26k lux for 24/0
-Additional info: Sorry, cannot measure PH in root zone. Everything was PERFECT until day 35. On day 35 I noticed 4 leaves, that look like the ones in pictures, but in a bit better shape. 5 days later - and a large part of the top canopy has become yellowish. Whether the progression is fast or slow, I have no reference point.


What have I done to remedy the situation?
1) Posted on forums
2) Reduced the PH to 5.55, because I suspected a micronutrient deficiency and iron/zinc get absorbbed better at lower ph. I dont think it helped.
3) Added a little bit more tap water to my reservoir. From day 37 to today the PPM of tap water in res is about 100.
a)Why did I add tapwater? I dont believe it is a PH lockout,I measured the PH regularly.... I suspected that 50 ppm of tapwater isnt enough MICRONUTRIENTS for a plant. And I think CANNA COCO line has very little to no micronutrients in their feeds.


P.S. Photos 6 and 7 used flash.


Thanks for at least rading this I suspect that a flush will be recommended anyways.

A general question. If you encounter a deficiency of my magnitude in COCO, do you just flush or try to fix it? From what I have read, it seems sometimes its easier to just flush, no?

BIG THANKS TO EVERYONE WHO COMMENTED ON MY ISSUE!!
I know its very hard to diagnose online ,I see this as a learning experience

 

[Talonxracer]

Are you letting the tap water sit for 24 hours to allow the chlorine to evaporate before using it with the RO water?

 

[BipolarBear91]

Are you letting the tap water sit for 24 hours to allow the chlorine to evaporate before using it with the RO water?

Yes, every time.
But I believe that my water would have to be EXTREMELY toxic to damage my plants , since tap water makes up only 20% of my solution volume and it starting ppm isnt extreme.

 

[St. Tom]

Yes, every time.
But I believe that my water would have to be EXTREMELY toxic to damage my plants , since tap water makes up only 20% of my solution volume and it starting ppm isnt extreme.

I grow in autopots bro and besides them top leaves she's looking good to me also I've grown with just coco but I feel coco/clay pebble mix is better I buy mine pre bagged in 50 ltr .also when you first started was you always feeding to run off before you ever put her on the res as I think you should remove her from it as I think she's locking something out with salt build up maybe as I often have 1 girl out of 4 throw a hissy fit so don't let this put you off growing as most things in coco can be fixed pretty fast

 

[BipolarBear91]

I grow in autopots bro and besides them top leaves she's looking good to me also I've grown with just coco but I feel coco/clay pebble mix is better I buy mine pre bagged in 50 ltr .also when you first started was you always feeding to run off before you ever put her on the res as I think you should remove her from it as I think she's locking something out with salt build up maybe as I often have 1 girl out of 4 throw a hissy fit so don't let this put you off growing as most things in coco can be fixed pretty fast

My previous failed 15 plants have givn me a PTSD.
I know that an auto can suffer irreparable damage in 10 days easily, if underyling issue isnt fixed.


You are right - in daylight in doesnt look as bad, but it looked MUCH better 4 days ago. I am afraid, if I dont change anything and just refill my res tomorrow as usual - 5.6ph and 600-700 ppm the yellowing will get worse and reach lower canopy...

Yes, I was feeding to 20-30% runoff in solo cups and also in 15 litre pots once I transplanted on day 13


P.S. You advise top feeding for some time? (In case I do a flush) I assume you cannot top feed after res has been turned on WITHOUT a flush beforehand,

 

[St. Tom]

My previous failed 15 plants have givn me a PTSD.
I know that an auto can suffer irreparable damage in 10 days easily, if underyling issue isnt fixed.


You are right - in daylight in doesnt look as bad, but it looked MUCH better 4 days ago. I am afraid, if I dont change anything and just refill my res tomorrow as usual - 5.6ph and 600-700 ppm the yellowing will get worse and reach lower canopy...

From an autopot grower to another remove her off the res for a start and let her dry out a bit you will know by lifting the pot when she needs it and I personally would just start top feeding her to run off every time for a while or you could even flush her with some lower ec feed never just water and that 90 pcent of the time will get me back on track also when your taking her off the res have a smell around her roots make sure it's not smelly just in case

 

[BipolarBear91]

From an autopot grower to another remove her off the res for a start and let her dry out a bit you will know by lifting the pot when she needs it and I personally would just start top feeding her to run off every time for a while or you could even flush her with some lower ec feed never just water and that 90 pcent of the time will get me back on track also when your taking her off the res have a smell around her roots make sure it's not smelly just in case

Wouldnt you say, that if, for whatever reasons, you decide top top water in middle of grow (after autopots have been turned on), isnt in very important to flush the salts that have accumulated at the top out first?

 

[St. Tom]

Wouldnt you say, that if, for whatever reasons, you decide top top water in middle of grow (after autopots have been turned on), isnt in very important to flush the salts that have accumulated at the top out first?

Yes I completely remove her her from her base part sorry bro I usually just turn my base upside down and sit her on that and sorry for any confusion