Actually, 50% is just right with lights on or off. I am guessing that you are venting your lights with a strong fan that is also sucking the humidity out of the room at the same time. What are your temps with lights on/off? You may be able to get a timer to control on/off times of your venting. Also if you have good air circulation in the room ( fans ), you won't have to worry about moldy buds with 50% humidity.