Howdy PAPA, The humidity, in my grow room, goes up at night as well. I run the exhaust fan and the circulation fans 24/7. I live in a semiarid climate (15% to 35% normally), but the grow room can get up to 55% to 60% when the ambient humidity rises outside. Keeping the fans running full time I have not had any bud rot or mold problems, so far.
Good luck with your growing.