I would probaly say that it just a stage of growth. there are lots of varity that turn purplish. I would would say if you did this couple days ago mold would not show that fast, could be wrong. I would not recommend spraying your plants at night because water will sit on them longer and have better chance for mold growth, Spray in the morning that way it will evaporate quick and have less chance of mold, also use a light amount of dish soap when use spray them the bugs hate that and get the leaves on underside. I would not do this a least a week before harvest thought might make your weed taste like soap. Bizzy