usually for me hour before bedtime-more common in early flowering if it is a strain that likes to double it's size. it's amazing how they are able to sense their surroundings and fill out the voids. I could swear 2 diff strains side by side-90% of the time one 'modifies' herself to look and represent more of what the other is. dwc is by far the quickest method but things can go sour fast-like a day versus week or so with soil. even quicker than drip and ebb and flow. maintaining the ph is the main thing. as they enter flowering, if you see changes in the ph consistently either higher or lower, than more than likely that is due to the plant using more of a nute or nutes, leaving the water either more acidic or basic. still havent figured out what causes what, but I can say for sure that if in DWC you are 4th week flowering and your ph is consistantly lowering everyday, good chance that it is P and K, maybe little N and MG. learned the hard way.