Neem!
Also spray unaffected plants to keep it from spreading.
I'm sorry I can't be more specific; my only experience with mold has been Black Spot and Powdery Mildew on roses, but neem works wonders.
stinkyattic Reviewed by stinkyattic on . Overnight mold!!! What to do??? I came into the grow room one day...Here is what I found...Help! Do I cut off effected leaves, harvest early, or Spray something on them. The plants most effected are in Hydro. I cut off some lower branches in order to show a good pik. So all you guru's can have a stab at remedy... thanks, latewood Just so you have all info...At the time I was flowering potted soil plants in same room...with a composted potting soil (black velvet), I never used before...humidity was around 60% Rating: 5