Possible potassium def. Need help diagnosing

[Dirrtybirdy]

I'm in week 3 and a 3 of my plants are starting to show what I believe is a potassium deficiency. I'm not too sure if it's that or the rockwool drying out too much. Listed below are the conditions of the grow

Plant - Blue dream
Light - spectrum king sk600
Nutrients - Jack's pure and clean ec is at 1.8 ph 6.0 - 6.2 (12tbs of the bloom formula and 2tbs of mag)
Temp - 78 degrees
Humidity - 55
Substrate - rockwool

Not sure if I'm missing any information, but I can provide more if needed.

Attached are some pictures.

Thanks in advance!

 

[Bundykid]

I had a similar thing, I didn’t end up diagnosing it, it was close to harvest so just battled through. Some good input from other growers though. Here is the thread,
https://www.rollitup.org/t/yellowing-of-upper-leaves-some-sort-of-deficiency.986618/

 

[hotrodharley]

That’s nute burn. Not a deficiency.

 

[Dirrtybirdy]

I'm going to do a flush next feeding then do a 1/2 feed and see what happens.

I also noticed that temps went up to 81. Could it be best stress ?

 

[Dr. Who]

Where did you get your use formula?

How about a completely known pre mix from bottle's?

Personally, I don't like their NPK values......Too much K and P. With K that stout, your reducing THC production...

 

[Herb & Suds]

I'm going to do a flush next feeding then do a 1/2 feed and see what happens.

I also noticed that temps went up to 81. Could it be best stress ?

A healthy plant can handle 81 f
You are chasing the result and not the cause

 

[JohnDee]

A healthy plant can handle 81 f
You are chasing the result and not the cause

Actually high temps can cause nutrient burn to be worse by increasing transpiration...thus pulling more (excess) nutes up to the leaves.
JD

 

[Herb & Suds]

Actually high temps can cause nutrient burn to be worse by increasing transpiration...thus pulling more (excess) nutes up to the leaves.
JD

Fair enough but I have a 4 light grow room and don't consider 81f high temp
It is my max temp in there

 

[Nutty sKunK]

Actually high temps can cause nutrient burn to be worse by increasing transpiration...thus pulling more (excess) nutes up to the leaves.
JD

Great info!

This is what happened to me on my last grow. Weren’t overfed. Just got too warm/dry which ended up burning the leaves as they were transpiring too fast.

 

[JohnDee]

Fair enough but I have a 4 light grow room and don't consider 81f high temp
It is my max temp in there

OK Herbs...got your point.. You are correct...81 isn't excessive.

Great info!

This is what happened to me on my last grow. Weren’t overfed. Just got too warm/dry which ended up burning the leaves as they were transpiring too fast.

I also learned that through experience. It's the top leaves that seem to be hit the worst.
JD

 

[Dirrtybirdy]

Where did you get your use formula?

How about a completely known pre mix from bottle's?

Personally, I don't like their NPK values......Too much K and P. With K that stout, your reducing THC production...

Im using their schedule they have online. I noticed earlier before I flipped that it needed more magnesium so I added about 1tbs per 40gal. I've tried bottled lines before, but I wanted to cut down on costs. Ive read a lot of good reviews about Jack's Nutrients so I figured I'd give it a try

 

[Obepawn]

I'm going to do a flush next feeding then do a 1/2 feed and see what happens.

I also noticed that temps went up to 81. Could it be best stress ?

81 is not overly bad but prolonged high temp can cause nute burn. When plants are heat stressed, they increase water uptake through respiration to cool down counter surface leaf temps. Well, a negative part of uptaking more water is extra nutes are also being absorbed by the plant. That is why during heat stress, it’s recommended you cut back on nutes and if you have an amended soil, you can get nute burn because it happened to me. Climate control is the most important thing there is.

 

[Hydro4life]

A healthy plant can handle 81 f
You are chasing the result and not the cause

My max temps when pushing co2 is 85!! You adjust feeding/ppm strength to match temp/humidity.

 

[Dr. Who]

My max temps when pushing co2 is 85!! You adjust feeding/ppm strength to match temp/humidity.

Not really.

As long as you stay within the VPD chart, you can run into the low 90's.... So the key is that chart and to run the corresponding RH.

 

[Dr. Who]

Actually high temps can cause nutrient burn to be worse by increasing transpiration...thus pulling more (excess) nutes up to the leaves.
JD

81 isn't that bad. If the RH is in the VPD range chart. Your basically golden.

 

[Hydro4life]

Not really.

As long as you stay within the VPD chart, you can run into the low 90's.... So the key is that chart and to run the corresponding RH.

Haven’t seen the VPD chart. Might have to have a look at it. Especially when dosing co2 you generally want higher temps (with the right rh) and powerful lighting to reap the benefits imo.
Will check it out Dr. who!! Cheers man

 

[Dr. Who]

Haven’t seen the VPD chart. Might have to have a look at it. Especially when dosing co2 you generally want higher temps (with the right rh) and powerful lighting to reap the benefits imo.
Will check it out Dr. who!! Cheers man

 

[Hydro4life]

Sooo easy.
I learnt through trial and error, always monitoring how much they drink and how much nutes they use. For example if temps increase and humidity drops and they don’t drink as much then the stomatas could be beginning to close making co2 enrichment a bit of a waste. Always reading the plants, and how they respond.
How much easier would it of been to have a chart like this at hand lol.

 

[Sobeit]

Had to same issue in one out of 3 ladies, using NO nutrients, tips curled up, yellowing. I assumed it was heat stress because of no nutrients or a deficiency, but the soil should be plenty for 4th week. I added in some seaweed extract to the foliage and a few days later to the roots. still waiting to see how she does, assuming heat stress N/deficiency, I also started up nutrients for them. One looks beautifully healthy, one with a few leaves fucked, and another growing in nicely.

 

[Sobeit]

Pretty sure it was showing signs of nitrogen deficiency. Gonna give it a week and see how she settles back in.