Hello everyone
it's week 7 of my second grow, Blue Dream auto-flower, 2x2 tent, MAXISUN PB2000 at 50% on 18/6, 5 gallon pots, 70 degrees, 50% humidity, PH unknown as i don't have the meter yet but i use filtered drinking water. i have 3 plants, all in same environment, same watering habit but the leaves of one of them which is actually a bit taller than the other two, has become downwards as seen in the picture (back left).
i know it may be due to several reasons but as per your experience, what is the usual cause? Thank you in advance. Piece.

Under-watered?