Yellowing bottom leaves in hydro

I'm wondering if anyone can help me on why my plants are turning yellow so quickly.

I'm on day 21 of flowering.
I have 3 different strains. Super glue. Ghost og. And Gelato.
Only the super glues are turning yellow.
I'm using hydroponics multiflow greentrees 2 gallon bucket system.
4x4 Rockwood covered in hydroton.
Ph is 6.4 in my reservoir.
I use a 3 part micro grow bloom. king kola , emerald goddess and honey chome products from emerald harvest.


Should I pick all the yellow leaves off ?
Also can anyone tell me if the buds look OK size for it being the start of week 3. Should they be bigger?

I put this in the wrong section. Trying to delete but I don't know how to.

Week 3 is the first P/K bump week btw they look N hungry. Stretch a lot first 2 weeks? #IMO

N def give more nutes? How many plants do you have? How many grow you right now

Don't give to much nitrogen in flower in bloom mutes is plenty need n for the stretch growing new leafs and stem

It sounds to me the strain thats having problems just needs more nitrogen. Its eating the bottom leaves to fuel its nitrogen needs. Some plants have different needs which sounds to me like this is the problem. once the growth stops nitrogen is not as important as other nutes.

Just looking at them, I would do a flush, and check the EC on the next runoff to see if they need more nutes. Looking at them I would say they need more.

pick all of the yellow leaves off so the plant can stop focusing on repairing these