Light burn or not?

[Grannygrow]

Hi all, my 1st grow forced into it with the lockdown, shuda started decades ago. I'm growing indoors in soil, tent 80 x 80 x 180cm. 600w HPS dimmed to 400w. Lights 22"-28" above the canopy. It seems 1 plant only is getting light burn or maybe not. Edges of fan leaves gone brown from the top. Other plants are fine. Any ideas? Cheers

 

[Mañ'O'Green]

@Grannygrow Welcome to AFN. We need to see the plants with pictures taken in Daylight 5000K or flash for diagnostic purposes. Turn off the grow lights.

A rule of thumb for HID lamps is the back of the hand test. Hold your hand palm down at canopy level. If the light on the back of your hand is too warm move the lamp up or dim it further.

 

[Grannygrow]

@Grannygrow Welcome to AFN. We need to see the plants with pictures taken in Daylight 5000K or flash for diagnostic purposes. Turn off the grow lights.

A rule of thumb for HID lamps is the back of the hand test. Hold your hand palm down at canopy level. If the light on the back of your hand is too warm move the lamp up or dim it further.

 

[Grannygrow]

Thanks, I'll take those pics tomorrow. Lights don't feel hot at all on the back of my hand.

 

[Grannygrow]

I reduced the lights to 250w yesterday. Although it didn't continue to brown, it continues to dry out (crispy). They are all fed & watered the same but the soil in the sick one is still wet while the others have dried out. The humidity is high 55%-70%. Only 1 small circulation fan. I defoliated them last Sunday but it didn't seem to bother them. Thanks for your time.

 

[Mañ'O'Green]

I reduced the lights to 250w yesterday. Although it didn't continue to brown, it continues to dry out (crispy). They are all fed & watered the same but the soil in the sick one is still wet while the others have dried out. The humidity is high 55%-70%. Only 1 small circulation fan. I defoliated them last Sunday but it didn't seem to bother them. Thanks for your time.

I am sorry but I still cannot see the problem in the pictures. Lets do this. I will move to the infirmary and see if others can see your issues. In the meantime.
Please fill in this form: (copy and paste part is below, this first one tell what specifically to include)

-Problem: (brief description)
-Medium/grow method: soil; soilless-- coco, or peat based like Promix, etc. (please provide the actual product name); DWC, NFT, etc.
-Feed and supplements used: include brand, dosage/strength, frequency of feeding and watering (alone); method-- by hand, drippers, rercirc' or drain-to-waste,... N-P-K #'s too if you can!
-Water source: RO/DI; tap- dechlorinated-?..... EC or TDS reading; pH (don't bother with this on RO/DI, do bother with TDS/EC though to confirm it's working well enough)
-Strain and age
-Climate: night and day ambient T and RH%; res' temperatures; any extremes in T/RH% exposure
- Light used: HID, LED, COB, combo of,... wattage; light cycle hours (20/4, 18/6 , etc.); distance to tops....
-Additional info: PH in the root zone. How long have the plants been affected?...How fast did symptoms appear?... Anything else you think might be relevant..

--Pictures including WHOLE PLANT PICS, and troubled leaves.. use normal light or flash as other light sources ruin color rendering, critical for diagnostics!

✂ - - - - - - - - - - -
(copy and paste)-->

Problem:

Medium/grow method:

Feed: and supplements used:

water source:

Strain/age:

light used:

Climate:

Additional info:

 

[Grannygrow]

Problem: Leaves browning at the edges & curling down. Dry & crispy. Initially thought light burn. Newer leaves becoming lime green between the veins. Only happening to 2 plants. Most affected plant does not seem to be absorbing water.

Medium/grow method: Soil, Plagron allmix

Feed: and supplements used: Plagron alga grow & alga bloom; Feed @ 1/2 recommended dose. No feed until week 3. Then fed 2 x weekly with Plagron alga grow for 1 week. Following week 1/4 alga grow 1/4 alga bloom. This week 1/2 alga bloom x 2. 6.5 PH in water. This week run off 7.5 ph

water source: Tap water, rural community scheme (no floride) Very hard water, high lime content. 6.5 PH. Water 7.5 ph this week.

Strain/age: Northern Lights feminized. Week 6

light used: Week 1 regular LED reading lamp. Week 2 -4 250w HPS. Week 5 & 6 400w HPS. Lights have never been hot on back of hand. Dimmed to 250w yesterday. No browning yesterday.

Climate: High humidity 60% -80% Temp 15° night 21°-23° daytime.

Additional info: Defoliated 1 week ago due to high humidity & threats of powdery mildew. All fan leaves except top ones & some small leaves that were blocking light. Plants bounced straight back grew 3cm next day. All looking good during the week. Plants now affected got most severe defolation. Most affected plant not absorbing water last 2 days.

 

[Mañ'O'Green]

@Grannygrow Ok now I can see it. That is not light burn it is a nutrient problem and it looks to be a potassium problem. But I think PH may be the main culprit here. PH should be 5.5 to 6.5 going in. I recommend to shoot for 5.8. You need a good PH soil probe to check the PH in the root zone. Get a Blue Lab Leap soil probe and meter or an Accurate 8 soil probe or the clone of it. Don't buy cheap ones they just do not work. Make small changes to the PH in the pot over a few days.

You started feeding a bit soon according to Plagron and should only be using the green sensation starting week 6 and Alga bloom starting in the 7th week?

Your night time temperatures are too low the minimum for best growth is about 20C below that will slow and even stop the growth.

Check the drainage holes on that pot and make sure you are not over watering it. That will cause nothing but grief. What you need to learn about watering will come with practice. Here are the basic rules: Never let the soil dry out. Soil and or coco can become hydrophobic if allowed to dry. This means it repels water. This in turn will create dry pockets in the soil and roots there will die. If your soil - coco have accidentally dried out use a surfactant to help re-wet it. I like yucca powder. Don't let soil remain soggy by watering too much too often. Root rot, damping off, molds, fungus gnats and other problems start in soggy soil. When you do water water the entire pot. How to learn when to water starts before you plant the seed. Fill your container with fresh soil/coco and weigh it (heft it) this is the lightest weight and consider it a dry pot. Now slowly water until the soil/coco will no longer absorb the water and run-off begins; weigh the pot (heft it) this is the maximum water, the wettest the pot can get. The difference between wettest and driest is the maximum water weight, for ease of explanation lets just say the water weighs 20 pounds. When the pot loses 10 pounds (half of the water weight) it is time to water again. There is an art to watering.

Soils that have a pre-charge of nutrients take practice to get right. It is difficult to know when to start adding nutrients - too soon causes lock-outs and to late starves the plants. If it is not the PH and the cold it might be an imbalance in the nutrients in the pot. Since you started adding alga-gro when the Plagron Allmix may already be heavy in those nutrients and the chart does not call for them at all. This might be locking out the Potassium so stop adding that and use the Alga-bloom at 60% strength. if this gets worse let me know and we will talk about flushing. Flushing is a last ditch effort with this kind of soil.

and keep me posted.

 

[Grannygrow]

Thanks a million Man O'. The dehumidifier & heater are on my shopping list this week. I gave the allmix a heavy wash out before using as recommended. I've also been letting the soil almost dry out before watering. I'll use lemon juice to lower the ph in today's watering. Should I give it to the healthy looking plants too? Really appreciate it. Cheers

 

[Mañ'O'Green]

Thanks a million Man O'. The dehumidifier & heater are on my shopping list this week. I gave the allmix a heavy wash out before using as recommended. I've also been letting the soil almost dry out before watering. I'll use lemon juice to lower the ph in today's watering. Should I give it to the healthy looking plants too? Really appreciate it. Cheers

Uhhmm you are not supposed to wash the Allmix it is a precharged product. Ok so lets treat this more like the Promix. See on the chart the suggested nutrients - use that instead. Well I guess it does not make any difference now because after week six they are the same regime.

Yes, continue to feed all of the plants and post some more pictures in a few days.

This is a tough one now from the stand point of where to go next. The problem with Potassium deficiencies is the toxic reaction looks the same.

This is a chart that shows some of the possible causes for a potassium lock-out:

Now I think we need to talk about your water as Ca Mg are some of the elements that can lock-out potassium. If your water is really hard over 300 PPM you need to cut it with some distilled water or RO. You need an EC meter to test your water to know if this is necessary. If it is then you may be able to get cheap water at the store in the self service machines that dispense water. It is .30 a gallon here. Then just mix in enough to your tap water to get under 200 PPM. Do you know if the water is treated with chlorine and ammonia? This forms Chloramines and should be treated with ascorbic acid - vitamin C. Not as critical in soil grows be needed in hydro. If it is just treated with chlorine no worries.