Can not seem to avoid this Potassium Looking deficiency issue after 2 weeks of Flowering.

[plumsmooth]

I do not remember this happening to me in the past. I have switched to high power LED i.e. HLG Scorpion Diablo and wonder if there is a relationship i.e. maybe my Leaf Surface Temperature is low. But I am pretty sure this happened even with my CMH.

I am going to do a side by side LED vs CMH since winter is coming. I will determine if this is a factor. I have tried all three of my current nutrients GH Advanced and Jacks. I tried lowering my PPM DS e.c. to the absolute minimum amount the plants are drinking in my RDWC thinking it could be excess since my plants usually go from drinking 1200 to under 700 right after the switch (.5 conversion).

And I have wondered if it could be an excess instead of a deficiency?

I have gotten lazy and have a tendency to top off instead of changing out reservoir as often as I should. I hear some people running bennies hardly changing out their reservoirs for a while?

One of my smaller plants didn't do it as much. Part of it is my plants are very big. However I modified my systems to have a 5X sized reservoir. IT is still happening. I grow in GH Power Growers. And I use lots of Beneficial Bacteria.

I have wondered if the Bennies are disturbing the Potassium somehow?

Luckily most of the leaves it happens to generally get defoliated due to my canopy profile and my LST configuration.

Nevertheless if anyone can please help me figure it out I would greatly appreciate it... The pictures I am including is exactly how it looks every-time on all of the plants. These are 1 lb harvest plants give or take. This Sour Kush is drinking like it has the potential to break 18 oz.

 

[RottyRzr]

I used to change out my res every 2 weeks minimum. there is no way to know what nutrients the plants are taking up and leaving behind. Could be an excess of something in the res. I have since switched to drain to waste and things have really improved. I haven't had that issue since. They get exactly what they need every time.
Hopefully someone will chime in with your answer.

 

[Piff_cat]

your first inclination was right. your transpiration rates have lowered due to a lack of infrared heat. potassium is needed in higher and higher levels thru the grow. the best solution is to add a heater or supplementary hps. or turn down your exit fan. increase your potassium or supplement your rez with sop- magnesium sulfate. bennies arent part of the problem they either help or are neautral

 

[Ca++]

Right at switch, the only real change is cooler nights.

 

[plumsmooth]

I used to change out my res every 2 weeks minimum. there is no way to know what nutrients the plants are taking up and leaving behind. Could be an excess of something in the res. I have since switched to drain to waste and things have really improved. I haven't had that issue since. They get exactly what they need every time.
Hopefully someone will chime in with your answer.

Even if it is considered more wasteful I really wish I could be on Drain to Waste I think that is the best way to be providing constant full range of available nutrients!!! Maybe One day

 

[plumsmooth]

your first inclination was right. your transpiration rates have lowered due to a lack of infrared heat. potassium is needed in higher and higher levels thru the grow. the best solution is to add a heater or supplementary hps. or turn down your exit fan. increase your potassium or supplement your rez with sop- magnesium sulfate. bennies arent part of the problem they either help or are neautral

How ever in Veg i sometimes see Calcium issues from cooler LST but why would it go to potassium right after the switch?

 

[plumsmooth]

your first inclination was right. your transpiration rates have lowered due to a lack of infrared heat. potassium is needed in higher and higher levels thru the grow. the best solution is to add a heater or supplementary hps. or turn down your exit fan. increase your potassium or supplement your rez with sop- magnesium sulfate. bennies arent part of the problem they either help or are neautral

So might lower Transpiration rates effect Potassium Uptake. Maybe the warmer leaf surface when I ran HPS and CMH is why I didn't used to have this issue! Damn it the whole reason I finally switched over to LED was to control heat mostly in the summer and warmer months here in Vermont. I swear the day I took my last Non-LED light down is the day I learned about Leaf Surface Temperature and realized keeping my 400 Watt Induction light on my young vegging plants was making them a lot healthier. Fuck electricity savings if I have to put the F#$%ing heat on in the summer. Anyway I was mad and now I have my Induction Lamp bak up generating nice heat for the space...

 

[jackspratt61]

So might lower Transpiration rates effect Potassium Uptake. Maybe the warmer leaf surface when I ran HPS and CMH is why I didn't used to have this issue! Damn it the whole reason I finally switched over to LED was to control heat mostly in the summer and warmer months here in Vermont. I swear the day I took my last Non-LED light down is the day I learned about Leaf Surface Temperature and realized keeping my 400 Watt Induction light on my young vegging plants was making them a lot healthier. Fuck electricity savings if I have to put the F#$%ing heat on in the summer. Anyway I was mad and now I have my Induction Lamp bak up generating nice heat for the space...

Try a boron foliar on a couple branches 2 days apart.

 

[plumsmooth]

Can you please elaborate on this Boron idea please?

 

[jackspratt61]

Can you please elaborate on this Boron idea please?

Use 50ppm boric acid spray two times over two days. Look for a response.

 

[plumsmooth]

Does not seem to match the Boron deficiency symptoms at all?

 

[jackspratt61]

Does not seem to match the Boron deficiency symptoms at all?

Does not seem to match the Boron deficiency symptoms at all?

Does the red midrib get more pronounced as the grow progresses?

 

[jackspratt61]

Add up all your calcium sources in ppm and multiply by .0055-.0085. Run the trials. I had same leaf symptoms. Have you noticed hollow stems?

 

[RockinRobot]

Try adding a little extra Epsom Salts. Or do a foliar with it

 

[Rodehazrd]

I went led and had everything deficiency I upped to more feed but still had calcium and potassium symptoms same mix and ferts worked well under hps
Any trick to get more Ca in early I’m all ears. Afraid of another failure I moved outside and haven’t used my room again yet.

 

[Three Berries]

Calcium Chloride is an easy quick Ca fix. 1500 ppm foliar or top dress is good.

 

[jackspratt61]

Add up all your calcium sources in ppm and multiply by .0055-.0085. Run the trials. I had same leaf symptoms. Have you noticed hollow stems?

It should be noted the nitrogen source matters in the above factors. I'm using 95% nitrate nitrogen.

 

[Weezard]

Just my 2 pennies. I had the same symptoms when I was gifted a very good, full spectrum, LED array.
Had to raise the light to a full 36 inches above the crown to resolve. Also solved the slow growth problem.
Cannabis stops growing at around 91k. Lux equivalent.
At around 95k Lux equivalent, some will "bleach".