If you water your plants at night..They will stay wet during the night and thus you will start to grow mold that will eventually harm your plants!! So water in the morning or when your light first turns on To prevent this from happening!! The water has all day to evaporate..=) Later
It depends on what kind of system you are growing in... Organic you should water when your soil gets dry...Try almost letting them wilt...Then water them ...this will tell you how often..Dont water if you dont need it..or you will be overwatering...You should mist them evenly untill they are fully soaked..I spray untill they start to drip alot... Hope this helps