Struggling, Top Of Plants Yellowing

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willowdog96

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Struggling here. I'm at the end of week two of flowering Ken's GDP. Generally, the plants are doing well; nice and bushy, flowers budding well, inter-nodal spacing great, roots nice and white. You'd think I'd be happy. What I can't seem to resolve is the yellowing of the leaves. I've boosted CaMg quite a bit and foliar fed them epson salts (safe, still early in flowering). I do regular change-outs and top up between. It's been 2 days since foliar feeding and I see no real change. It's possible they could be locked out but I do know transpiration is taking place as water is being consumed; maybe that's not correct though.

Any thoughts would be appreciated.

I'm growing indoors in hydro. LED lighting (I know they're not too close). Room temps range from 75-80 and humidity is 45-55 depending on lights on/off. My pH is 5.8; double checked. Water temp is 68. EC right now is 1.2 (840 ppm700). CCH2O nutes.
 
Struggling top of plants yellowing
Struggling top of plants yellowing 2
Unit541

Unit541

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Mg will generally show up on older, lower growth first. Your stats seem to be in check, but there are a couple of unaccounted for variables. Namely light and water. Are you using R/O or tap? Could be some other micro-nutrient deficiency. A zinc or manganese deficiency can look sorta like that, as can Iron.

I know you mentioned that you know your LED's aren't too close, but... did the plants veg under these lights as well? Can you think of anything that changed close to the time the condition started?

In my own garden anyway, it's always been one of three things anytime I end up going in circles trying to solve some mysterious leaf appearance. PH, RH, or a motherf*cking LED that I knew was the perfect intensity at the perfect distance.

I suppose bugs of some sort are a possibility, but I try not to be too quick to jump to that conclusion without seeing them directly. The margins of the leaves aren't super happy either... and the tips, I can't tell if they look yellow or brown. I've had some plants that would only indicate a P def. with brown, up-curled tips, in which case they may just want a bit more EC, which wouldn't be unusual if you're using RO.

In the end though, it sure seems PH related if you consider all the signs the plant is showing. You said you're in "hydro", but didn't elaborate. Growing in buckets? Coco? Rockwool? Any other inputs besides base nutes? This all matters a lot.
 
Enforcer

Enforcer

2,008
263
How long has it been since you calibrated your PH pen? I’m thinking you may be a little lower than it says and your locking out Magnesium. I would raise the PH to 6.0 and see if she responds.

My only other thought was light burn since it’s highly localized at the top of the plant. But your stats all look good, so I’ll assume you also know how far away to hang a light.
 
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willowdog96

13
3
Mg will generally show up on older, lower growth first. Your stats seem to be in check, but there are a couple of unaccounted for variables. Namely light and water. Are you using R/O or tap? Could be some other micro-nutrient deficiency. A zinc or manganese deficiency can look sorta like that, as can Iron.

I know you mentioned that you know your LED's aren't too close, but... did the plants veg under these lights as well? Can you think of anything that changed close to the time the condition started?

In my own garden anyway, it's always been one of three things anytime I end up going in circles trying to solve some mysterious leaf appearance. PH, RH, or a motherf*cking LED that I knew was the perfect intensity at the perfect distance.

I suppose bugs of some sort are a possibility, but I try not to be too quick to jump to that conclusion without seeing them directly. The margins of the leaves aren't super happy either... and the tips, I can't tell if they look yellow or brown. I've had some plants that would only indicate a P def. with brown, up-curled tips, in which case they may just want a bit more EC, which wouldn't be unusual if you're using RO.

In the end though, it sure seems PH related if you consider all the signs the plant is showing. You said you're in "hydro", but didn't elaborate. Growing in buckets? Coco? Rockwool? Any other inputs besides base nutes? This all matters a lot.

My hydro system is buckets with rock wool as medium. I am using RO water with UV. I keep thinking LED but have raised them to no affect. I feel fairly confident in my pH but it does want to drift downward even right after a water change. Roots look pretty good too.
 
Jmaes Mabley

Jmaes Mabley

675
143
Kinda looks like a PH/Zinc Deficiency.
G

In general, zinc deficiencies are more likely to appear when a grower is using heavily filtered or reverse osmosis (RO) water to feed plants since any zinc has been removed, but pH is a much more common reason growers see zinc deficiencies in their cannabis plants.


If your PH is good, Id look into some micros.
 
Unit541

Unit541

234
63
Why are you using RO? What's wrong with the tap? If it's just way to hard, mix it with your RO before adding nutes. If however, your tap comes out .5 EC or under, then move your RO filter up to the kitchen, drain your reservoir, mix your nutes with tap water, and watch your problems disappear.

The topic of RO water is not discussed intelligently enough, and there's this terrible misconception, that it's always better than tap water. RO water should be used when the requirement for such has been established, not simply because it fit in the budget when the grower went on the initial shopping spree. Generally speaking, those that are successful with RO, are not your average off-the-shelf-from-the-grow-store gardeners. They've spent a serious amount of time figuring out their nutrient profile, accounting for every last micro nutrient required, and every thing in specific ratios to one another. When you just want to dump something out of a bottle into a bucket, the micros and ph-stability of tap water will keep you in the "easy zone".

If you absolutely must stick with RO, attention to your nute program is in order. They're not getting something they need, and it's either because it's not present, or present and unavailable. Both of those come down to whats in the solution.
 
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willowdog96

13
3
Why are you using RO?

Well, good question. I was under the impression that the starting with a clean slate, so to speak, was easier not harder to balance nutes in. That said, you raise a good point.
 
H

heisen

2,626
263
Why are you using RO? What's wrong with the tap? If it's just way to hard, mix it with your RO before adding nutes. If however, your tap comes out .5 EC or under, then move your RO filter up to the kitchen, drain your reservoir, mix your nutes with tap water, and watch your problems disappear.

The topic of RO water is not discussed intelligently enough, and there's this terrible misconception, that it's always better than tap water. RO water should be used when the requirement for such has been established, not simply because it fit in the budget when the grower went on the initial shopping spree. Generally speaking, those that are successful with RO, are not your average off-the-shelf-from-the-grow-store gardeners. They've spent a serious amount of time figuring out their nutrient profile, accounting for every last micro nutrient required, and every thing in specific ratios to one another. When you just want to dump something out of a bottle into a bucket, the micros and ph-stability of tap water will keep you in the "easy zone".

If you absolutely must stick with RO, attention to your nute program is in order. They're not getting something they need, and it's either because it's not present, or present and unavailable. Both of those come down to whats in the solution.
Very well said
 
Unit541

Unit541

234
63
Confirmed, my tap water is about 0.4EC; a tad high.

Hey that's great! .4 is fine. Some poor bastards are getting like 1.6 out of the tap. Use your perfectly awesome tap water instead of your RO. Reduce your calmag a bit to account for the higher starting EC.

Again, for all those considering (or currently using and having problems with) RO, ask yourself why you're using it. The answer to this question may just save you an immeasurable amount of time and frustration. If your using it because your tap water EC is so high that there's not enough "room" left to add enough base nutes, then it's time to accept that nutes from a bottle aren't going to be the best bet.

If however, your tap is under .5 EC (~250ppm .5 scale), then there's no issues with your nutes, and the inherent PH stability of the tap water is going to make your life much easier, and your plants much happier.
 

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