Not sure, I have always had some fan funk. We have talked about it a bit before, but never got to the root of it. I am off the floor with sheet insulation under my tent, so I don't suspect it's heat or cold from a foundation coming through. I checked for bugs and it does look like I have springtails, but from what I read they are nothing to worry about, but about a week ago I started giving small doses of Azamax to the plants because that's honestly the only thing I can figure it could possibly be.
Try upping feedings about 20 to 30%