plants need a few hours 4 or so id say @ least to respirate, yes if they are too far from the light they will get leggy, w/ the exception of the really intense lights an inch or two away is perfect, good luck! btw, the only recognizable difference between plants producing anthocyanin is a slight increase in astringency or acidity! some scientific research has shown that the antioxidant flavonoid has the possibility of anticarcenigenic affects as well as improving eyesight, having anti-inflamatory properties, reversing the effects of high blood sugar(diabetes) on the renal and nervous systems, ( im sure you have heard of the health benefits of antioxidant fruits like blueberries and pomegranites, dark fruits are very high in antocyanins)Also they have done studies on the increase in stomach mucous link to anthocyanins, which help to protect from ulcers and other damaging conditions like acid reflux.anyway it wont hurt your plants at all, id be more worried about how leggy they are, but you can fix that by burrying them up tho the first set of leaves. good luck!