During the light hours the closet door stays open. There is a 16 inch fan blowing out of the closet during the light on hours and at night there is no "ventilation" I do keep the fans running in the closet at night, but theres no exhaust or intake. The Second fan is a 4 or 5 inch fan in the rear of the closet. Note the big fan isnt blowing directly on the plants, but away from them towards the closet door. Immediately left to the closet is the bathroom where I leave the exhaust fan running 24/7. I also leave the bedroom windows cracked. Never got a ... barometer? or whatever meter you use to read humidity but that could definitely be it. But its not happening on all hte plants which is a stumble:|