Necrosis & red stems - Signs of potassium deficiency?

[BillyWu]

Hi folks. My plant has started doing the same thing it did on my first grow - the leaves are yellowing and brown necrosis spots are appearing. The leaves are going crispy also. I have been wondering what this was for quite a while but I finally found it. I believe it is potassium (K) deficiency, but I just want to get some clarification so I can treat it adequately :]

Lights: 250W HPS, 2x 50W UFO LED leds about 12-14" from the light source
Pot size: 20 litres, soil (BioBizz light)
Soil pH: Last measured at 6.5 on my last watering
Strain: Think Different
Last feed strength: 1.1EC consisting of 1ml/L BioBizz grow, 2ml/L BioBizz bloom, 1ml/L BioBizz topmax, 0.5ml/L Liquid silicone, 1ml/L CalMag supplement, 0.1 EC pH 7 tap water
Other notes: Using a ScrOG

I'm pretty sure it's potassium deficiency. I have recently just got some 0-17-38 Bloom feed (Dr. Hornby's Big Bud powder) to feed my plant, I believe this will provide the necessary potassium to fix the problem. Just to be sure though, here are some pictures from my previous grow showing exactly what is happening in my current one:

As you can see, the leaves are yellowing, curling up brown at the ends (which becomes dry and brittle) and large brown spots across the leaves.

My current plant is at day 52 I think, this other one was about day 60.

 

[Muddy]

P deficiencies can be quite common in late flowering. I always keep a bottle of PK13.14 around just for that. How old are they? Looks like they could just be finishing up.

 

[BillyWu]

Day 52 I think.

 

[agito]

or just up the bloom mixture up 1ml

red stems can be temp or genetic as well

be fair it look like N to me

light mix your suppose to go harder with the grow according to the booklet

 

[BillyWu]

or just up the bloom mixture up 1ml

red stems can be temp or genetic as well

be fair it look like N to me

light mix your suppose to go harder with the grow according to the booklet

Temperature is a consistent 80-85 degrees Fahrenheit in my tent, plus I grow with CO2 so temperature is only an issue if I go above 95 degrees. I water with 70 degree Fahrenheit water, so essentially room temperature or just over.
I'm not sure about Nitrogen deficiency bud. According to this chart, nitrogen deficiency doesn't cause necrosis.

The only thing I can see on there that could be causing the problem is potassium or magnesium, and it's most definitely not magnesium because I don't have white leaf tips, I use CalMag supplement and my pH is a perfect 6.5. Potassium is what I think it is due to yellowing leaves, red stems and necrosis on leaves.


Just gave her a watering with a standard solution of Dr. Hornby's Big Bud powder, 0.5g/L with 3 litres of water, gave me an EC of 0.67.

 

[agito]

not sure about the hornby but organic nutes contain far less chemical salts so ec is a not accurate measurement

by going to low on grow you would still reduce the whole npk as grow contains all NPK the uniform yellowing looks like N but to be fair the whole plant could just be under fed rather than singling out a single nutrient

at this point and this media most would be running 2ml grow 3ml bloom min (total 5-6ml) vs your 3ml all points to underfeeding as a possibility

it looks like ph as multi elements are showing at once

I have different charts saying different things

 

[BillyWu]

Yeah I was considering it may be underfeeding but I'm not sure, I don't like upping concentration too much as it's quite a substantial jump in strength to take in all at once, makes it difficult to gauge how the plant will react unless it gets burned or doesn't.

True, they may contain less chemical salts but EC is a good way for me to measure the overall strength of the nutrients I'm adding to my plant. It's worked quite well so far.

Agito I really don't think it's pH. I just got the run-off again and it's 6.5 still.

 

[agito]

not saying its ph
just typical ph lockout show muti elements missing (lock out)
under feeding shows multi element missing
they would look the same
up the grow by 1ml and monitor it
not saying do this but a full strength feed on here is 8ml per lite so going to 4 is half strength

 

[psykadelix]

Those leaves are fuukkked. But you're late enough I'd say just add some of that bloom shit but not too much as when the leaves can no longer hold nutrients they go right into your bud and give it that leafy taste like you're smoking spinach.

EDIT: Those buds look great btw:clap:

 

[BillyWu]

View attachment 140227not saying its ph
just typical ph lockout show muti elements missing (lock out)
under feeding shows multi element missing
they would look the same
up the grow by 1ml and monitor it
not saying do this but a full strength feed on here is 8ml per lite so going to 4 is half strength

Ahh, that chart is what I've been missing! Thanks Agito, I'll up the strength and see how it goes :] Much appreciated.

Those leaves are fuukkked. But you're late enough I'd say just add some of that bloom shit but not too much as when the leaves can no longer hold nutrients they go right into your bud and give it that leafy taste like you're smoking spinach.

EDIT: Those buds look great btw:clap:

Thanks man, but that was my first EVER grow that made the Dutch Passion Hall of Fame :] My current buds are looking like this: