Water will be evaporating from your plants in a very closed space. If you don't have an RH controller, you should just leave the fan on, otherwise, your tent will get all sweaty and then MOLD.
I would get an RH controller myself if I didn't just string my stuff up across the ceiling in here with no regard to smell or humidity, and put it up when its "pretty dry", ie, sugar leaf pulls off easily and with a light snap.