Potassium Deficiency or Magnesium?

High Guys
Hope you can give me some clear sight about my lower leafs.
20 gal pot on 3x3ft with LED Lights and alright temp and humidity. Day 22 of Flower in a Croots Mix which is used now 3 times in a row with topdressing after each run.
Everything is going fine so far but I found some leafs to change this morning and I am worring a bit because I can't identify it properly.
Hope you can help me ))

Looks like K def to me. The edges yellow then burn on the lowest growth. Makes sense since it’s beginning to flower.

Add a source of K if possible but since it’s a living soil might take a while for the deficiency to stop progressing

Perfect
I gave her some Potassium and everything turned out fine.
I have another plant in a seperate Box which is in a Hempy bucket and it is showing similar problems. Would you agree with me?
Hope you could give me your advice again
100% perlite hempy day 18 of flower
EC 1.55 starting from 0.2
PH input 5.7
Output 6.2
I would say these are clear signs of a hungry plants but I would ask for a second opinion before.
The difference is that this plant is turning somehow light green as well.
Thank you so much to help me out

Looks hungry and the K def is likely from a low PH.
Ive attached a great chart showing the timing of a plant’s specific nutritional needs.

Cocktrauma said:

Perfect
I gave her some Potassium and everything turned out fine.
I have another plant in a seperate Box which is in a Hempy bucket and it is showing similar problems. Would you agree with me?
Hope you could give me your advice again
100% perlite hempy day 18 of flower
EC 1.55 starting from 0.2
PH input 5.7
Output 6.2
I would say these are clear signs of a hungry plants but I would ask for a second opinion before.
The difference is that this plant is turning somehow light green as well.
Thank you so much to help me out

Click to expand...

You should be feeding at around 3ec at this stage. Output should be 4-5 ec

what is your ec coming out?

what strain is this and what are feeding?

It's K. I'm seeing shiny leaves and nice green leaves, so it's not N or P, or Mg. Gotta be K.

Cocktrauma said:

Perfect
I gave her some Potassium and everything turned out fine.
I have another plant in a seperate Box which is in a Hempy bucket and it is showing similar problems. Would you agree with me?
Hope you could give me your advice again
100% perlite hempy day 18 of flower
EC 1.55 starting from 0.2
PH input 5.7
Output 6.2
I would say these are clear signs of a hungry plants but I would ask for a second opinion before.
The difference is that this plant is turning somehow light green as well.
Thank you so much to help me out

Click to expand...

They still have a K deficiency.

I've reduced to EC 1.0 and they are doing fine now.
But you are right it's probably K but because of to much fertilizer.
EC 3 would be killing them straight away....