Severe yellowing in flower

Room:

Sealed 1500 PPM Co2
Temps = 74-78
Humidity 30-50%
Nutes: FloraNova
5 Gal buckets
Soil PH 6.0-6.2 measured via direct soil Blue Lab meter
RO Water with 5ml/gal of CalMag
Bugs: Minor fungus gnat problem.
Soil: sunshine mix #4


I have been going much lighter on the nutes than I usually do in both Veg and Flower, typically 1/2 the lucas formula recommended and barely any nutes at all in veg (they seemed healthier). I would consider myself a fairly experienced grower and I have flowered out the same strains numerous times. My plants started to severely yellow 4 weeks in flower. Knowing that root aphids can cause a similar problem I spent the last two days inspecting every sticky trap for for root aphids under a microscope and tons of leaves and I confirmed that there are only some fungus gnats in the room (being treated w/BTI) and no root aphids (I have never had aphids). I even pulled root ball out to inspect it for possible aphids but there are none to be seen and the roots appear healthy. I just gave the full lucas formula to the plants and doubled the dose of calmag and now I'm waiting to see how they respond but I hope that someone might be able to share their same experience to see if I made the right choice. My other thought was that they might be root bound but they don't particularly look root bound (see pics). One odd thing I noticed is that the leaf veins appear to be yellow while the margins appear to be green on the leaves that are still transitioning to yellow which is completely opposite of a magnesium or iron deficiency so it seems like simply nitrogen but it's surprising that it hit so fast.

I don't know how they're growing so well with that PH...it's supposed to be 6.5 to 7.0 for soil, but they look good for that PH level...I'm lucky, my tap water is 6.6 on the dot and my nutes only raise it .2, so I don't even check it anymore..
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You still have plenty of time to feed them some N and raise that PH....green leaves make big healthy buds

When I say soil PH I mean the actual PH of the soil, I feed with 6.8-7.2 PH. Pro-mix and sunshine mix use peat which drag the PH down without you even realizing it (even with added lime).

RIKNSTEIN said:

I don't know how they're growing so well with that PH...it's supposed to be 6.5 to 7.0 for soil, but they look good for that PH level...I'm lucky, my tap water is 6.6 on the dot and my nutes only raise it .2, so I don't even check it anymore..
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I'm hoping it's just an N problem and the floranova bloom has a decent amount of N in it so it should take care of it. I don't expect any of the yellowing to reverse but hopefully it doesn't progress. I'm concerned that I'm not thinking of something because based on the progression I need to act quick if it's a more serious problem.

RIKNSTEIN said:

You still have plenty of time to feed them some N and raise that PH....green leaves make big healthy buds

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Do yours always look that yellow in flower? Was that pic mid flower? Maybe this much yellowing is normal and I'm just used to over nutted plants. I always expect some yellowing but my current flowering plants look 50% yellow and it's only mid flower.

RIKNSTEIN said:

I don't know how they're growing so well with that PH...it's supposed to be 6.5 to 7.0 for soil, but they look good for that PH level...I'm lucky, my tap water is 6.6 on the dot and my nutes only raise it .2, so I don't even check it anymore..
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Most likely your on the right track. Not enough n in the nutes your using and most likely to much k which is locking out your N. what are the NPK values in the nutes your using ? Like you said a good flush and then a good feeding with N should get you back on the right track. Contrary to what most say around here you do not want your leaves to yellow at the end of flowering. Just like you don't want to flush your plants at the end. Don't do it. And dont worry to much about ph in your water. Soil has a great buffering ability so dont worry To much about that. Check out this site that gets posted a lot. http://www.totalgro.com/concepts.htm Hope this helps good luck

Like Daze said forget about ph this is N deficiency. Just increase N and lower P n K and they'll be fine.

hard to tell from your pics under hps,
if you are getting rapid yellowing from 4 weeks onward of flowering when the plants previously looked healthy and green
this can often be caused by heat and environment ,
you are growing in a sealed room with co2 enrichment , i think this would be the best place to start checking for problems,

when plants have N deficiency they often would go light green, they would show signs over a long period, rapid yellowing
can also be caused by over watering
do the leaves look like they are going crispy too ?

I think we are having the same problem. The problem with us is that we are using a one part nutrient, and we can't just increase N.

Check out my thread, mine are also yellowing, and I thought adding more nutes would help because FloraNova bloom has N in it. But I ended up burning them.

Skunkd0c has some good points. But still the NPk values of the nutes he is using will say a lot. Like if he is using enough N. If not then of course his leaves will start to turn yellow over time. Better fix it now before its to late. But could be the points mentioned either as well. Has anything changed in the environment lately? Better check all growing conditions first. Good points

Also, Ive read that with a high level of c02 enrichment like you have, the temps in your room are supposed to be in the mid to upper 80s. Something about the temps needing to match the plants having a faster metabolism with the c02. Maybe that could be effecting the nutrient uptake.

All I can do right now is wait. The yellowed leaves don't respond too well to nutrients but I don't expect them to, all I can wait is for the yellow leaves to die and fall off. When the soil dries out completely I'm going to hit them with a decent hit of CalMag+ which is 2-0-0 to give them a touch more of nitrogen.

FloraNova bloom is 4-8-7 which is what I use

doujadaze said:

Skunkd0c has some good points. But still the NPk values of the nutes he is using will say a lot. Like if he is using enough N. If not then of course his leaves will start to turn yellow over time. Better fix it now before its to late. But could be the points mentioned either as well. Has anything changed in the environment lately? Better check all growing conditions first. Good points

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Normally I expect some yellowing, just not that much. It happened over the course of a week. Temps in the room have never exceed 82*F which is pretty low for C02.

skunkd0c said:

hard to tell from your pics under hps,
if you are getting rapid yellowing from 4 weeks onward of flowering when the plants previously looked healthy and green
this can often be caused by heat and environment ,
you are growing in a sealed room with co2 enrichment , i think this would be the best place to start checking for problems,

when plants have N deficiency they often would go light green, they would show signs over a long period, rapid yellowing
can also be caused by over watering
do the leaves look like they are going crispy too ?

Click to expand...

The main thing I was doing differently was feeding less in Veg. I probably only fed them 2-3 times their whole life prior to flowering so I have a feeling the leaves store a lot more nutrients than I originally thought.

doujadaze said:

Skunkd0c has some good points. But still the NPk values of the nutes he is using will say a lot. Like if he is using enough N. If not then of course his leaves will start to turn yellow over time. Better fix it now before its to late. But could be the points mentioned either as well. Has anything changed in the environment lately? Better check all growing conditions first. Good points

Click to expand...

i mean i dont think that it to bad if the ideal for bloom is a 1-3-2. There is N there so some of these other post about the C02 or environment is something to look into, and your right those leaves are probably not coming back. Try what you said and give em a good dose of N and see what happens. Might just be the watering or overfeeding depending on schedule. How often are you feeding might be the key. Good Luck

In flowering when this starts to happen so aggressively it means something is being locked out,now obviously everyone is screaming N P K in which neither are the problem,you need micro nutes soon your leaves will whiten and fall off or other problem will start happening,someone who posted before me was right about your PH imbalance which is making the iron(fe) unusable so it builds up.Feed at half strength but your main objective is to get the PH to 6.5-6.7 with no fluctuating.

I'm going to let everything dry out pretty good then water it with with RO and calmag and nothing else. It will probably take 3-4 more days for everything to dry up.