m0useanswered grow question a year ago Few options to increase RH in a environment.
You can have buckets of water open and they help evaporate into the air.
Same idea but you soak a towel in water and hang it in the tent, more surface area to speed evaporation. I've done this before and it works well but you need to re wet the towel once or twice a day sometimes.
Best lazy option is get a humidifier for the main room the tent pulls air in from. then its RH will stabilize the main tent acting like a lung like room.
Good Luck!