I havent had any problems until now. I assume it has to do with 3 being in preflower and one flowering. I am growing in 5 gal. pots using coco coir and fox farm trio with calmag+. My oldest plant the is one of the gg4 it was developing some brown spotting on the leaves but since I am battling nats i didnt think much of it. Now all four plants now have yellowing and browning leaves at the bottom of the plant.