What could've cause this problem?

[Ovah]

One week into bloom.
The plant is taking up nutrients, water smells ok, roots looking fine.
I need a new PH monitor, but never had problems with PH before with the same usage of nutrients I gave the plant now.

Any ideas?

 

[jfarrismu]

Potassium deficiency possibly

 

[Ovah]

Potassium deficiency possibly

Agree.
I ran out of my AN Jungle Juice series which i've been using for years without any problems and had some AN PH-perfect that I hadn't used for vegging this plant.
I was away for a week, opened the tent the plant had grown much bigger but a lot of leaves was drying up and looking shitty.
Changed water with PH-perfect, checked the EC when it was time for that and saw that it was low even though I used the same amount I use with Jungle juice series.
But apparently PH-perfect is much "weaker" so the plant probably didn't get enough.
Sucks because you have to use a shitload from the PH-perfect to reach the desire EC and most vendors don't sell Jungle Juice series anymore...