Im sure there are no light leaks. so plant moisture stress might be the problem, it gets pretty humid in the room. what would be a good way to reduce humidity without having to buy a de-humidifer.
do you leave the ventilation/circulation going all the time or have you been turning it off.
The circulation runs 24/7
ventilation runs periodically during light on hours
Get yourself some Calcium Chloride, its the stuff that is in damp rid I am sure you can find a big bad online for a good price.One other idea, you know those silica ball gel packets you see in packages of beef jerky and what not? the purpose of those is to remove humidity from the air. I've heard of people using them on a large scale like with what your doing. Might want to check those out.