Indoor Mg Deficiency or...?

[beachbuds]

Problem: Yellowing leaves on new growth.

Medium/grow method: OF + 3tbs topdressed dolomite lime on week 3, 3gal fiber pots

Feed: and supplements used: Tiger bloom/big bloom half strength for about a week now, 1/3 gal/plant every 2-3 days, bottom fed until no more wicking seen in 60 min. Excess liquid is removed from trays but usually there isn’t any. pH 6.3 of nute solution by pH strip. Dripping blumats continually with tap water only, dialed back so they don’t kick in until the pots are pretty light, using about 1/3 gal per plant per day when running unless I bottom feed then they shut off completely.

water source: garden hose tap, pH 6.5 per my measurements with pH strip. City average data from source (lake) from 2018 (latest year available, average reported): pH 7.8, 390tds, 130 CaCO3 ppm, 200ppb boron, 52ppm calcium, 25ppm Mg, 3ppm potassium, 30ppm sodium, 233 ppm total hardness, 163 ppm sulfate.

Strain/age: MoAB, Caramelicious, Jackberry Day 47

light used: 600w Vivosun, bloom and veg switches on, 18” away, 24/0.

Climate:20-24c, RH 50-70%

Additional info: pic taken with 23w 6500k cfl. All plants showing slight yellowing but MoAB (back right of the trio shot, closeup leaf pic) is most obvious. Spent time researching as much as I can using self guides but still uncertain since This is my first grow ever. Seems like either a Mg or maybe an iron issue from the pics...? It’s showing on the new growth only from what I can tell.

Thank you in advance. This forum is such a great resource, much gratitude!

 

[beachbuds]

Update: popped open new pH strips across the range of 7-10 and they reported my tap water closer to what the city states, 7.8. Damn. Was using older strips across the 4-7 range before. Current theory is the high pH in combination with Big Bloom (NPK 2-8-2) may be driving iron lockout. Given that it’s on new growth and old growth is not showing any signs of intervenial chlorosis, leaning towards this as the diagnosis. Just placed an order for pH up/down, Apera pH 20 meter, and EC/TDS meter. Dropping the strips, not reliable.

Treatment suggestions?

 

[Arthur]

I didn't see a cal/mg on your feed list. Under led, better get it on the shelf, you'll need it.

Treatment really depends on what the reaction of the soil is. Lime tends to raise pH, before going farther, I'd check the soils pH, if it's still 6.2 to 6.8ish I'd adjust my feeds and carry on. Cal/mg is something you'll probably need as well, Cannabis can be cal/mg hungry to start with, under LED it's a pretty much seems to be a necessity.

 

[beachbuds]

Cal/mag is not on the feed so far. It’s represented in my city water at 52pmm Ca and 25ppm Mg already so wasn’t sure if more needed to go in...? Is there a known spot range for these in nute mixtures for soil?

Dug the MoAB out to have a closer look and trimmed a bit. Look at the contrast of the older fan leaves to the new growth from the deeper shaded center of the plant. Thinking the deep shade is what’s causing it to be so light, but I could be wrong...? Is this an indication of anything?

 

[Arthur]

Twisted growth makes me lean towards a calcium deficiency. The paleness could be magnesium. The mg you could use a little epsom salts, its early, not mid flower or after... the sulfur won't make things smell or taste purdy. Calcium is most available somewhere 6.6 up, so your either low on it, or out of range.

Now that I see your I fox farms, you need to check the pH of your soil. I dropped them a little over 2 years ago, unstable pH issues. I'd get about 6 weeks and the pH would drop into the mid 5s.

 

[beachbuds]

OF risks and and the critical importance of accurately knowing pH learned on grow 1 at least. All my pH readings could be wrong due to these strips, which if that’s the case, sends this whole thread into suspect zone. I top dressed with the dolomite line at week 3 because I thought runoff was pH 5.1and I had read numerous stories about the acidity issue of OF. Seemed to be ok for a few weeks except for the fungus gnats issue that was pretty easy to deal with by adding sand. Regardless, plants looked great and were growing well. Then the yellowing leaves issue started. The other lesson learned is how important a good soil blend is from the get-go. Dealing mid-grow with shit like this is a pain in the ass.

Getting a legit pH and ppm meter today along with some real buffers so before I go into supplement mode with Ca, Mg, etc I figure I need to get accurate pH values of my tap, my soil, and my runoff and establish a real baseline. If it’s indeed super alkaline like the strips say, thinking pH 6 flush followed by proper pH 6.5 feeds with some cal/mag and I could be back on track. I’m hopeful that will release any lockout issues and get them going again. I’m wondering if the slow flowering development is also related to a high pH issue? I’m almost on D50 and barely any pistils on these autos. Calyx are there just not much development. Again, first grow and no idea what this strain is like. My gut says the whole grow seems paused right now. The pic below is from the best looking Jackberry main bud site, it’s trying I think

 

[Arthur]

If the pH went down, definitely could effect flower production. Phosphorus really doesn't start doing its thing till 6.4.

 

[beachbuds]

Picked up an Apera pH 20 and a ppM meter. Turns my tap water was pH 7.8, 465 ppM. Adjusted tap down to 6.5, flushed plants with 2 gallons each. 20 min after second flush measured pH runoff on each plant. Came in at 6.7 on all the plants. Hopefully back on track now. High pH issue of the water has me doubling down on the iron deficiency as the cause, time will tell. Got some cal mag anyway just in case.

Question: after using pH down to adjust my tap water to 6.5, my ppM goes to 525. Is this insanely high to use? I haven’t checked it with any of the big bloom/tiger bloom nutes in it yet either but it’s obviously gonna go up. I do have a basic home RO water system that comes in pH 6.5 and 25ppM TDS. Was thinking tap was better as it had all the inorganic tds already in it, but 525...? Is that just stupid high for a water source?

 

[Epicxr]

Thats insane 500 ppm is 1.0 EC only just got one of my girls on this level myself. my tap water is anywhere from 7 to 30 i use leds too and have to use calmag myself they like it

 

[beachbuds]

Does ppM of water really matter all that much if growing in soil? Is there an upper absolute limit for tds that is simply too much?