Dark Room Qs!

Recently ive switched from 24/0 to 20/4. (the girls seem to love their nap time)
Im not using a timer for my lights due to the fact that i have different aged plants/seedlings in my grow room.
My question though, is a dark room ok for my plants to transfer to when they go for their sleeping time?
The dark room is a completely sealed off, clean closet where no light can leak through. Also should i put a fan directly on the plants while their sleeping? I already have an exhaust fan for fresh air to get in.
Please any response would help
thanks all.

if u have ur lite schedule at 20/4 then ther alrdy in the dark for 4hrs wats the point of moving them to another dark room? seems to me ur creatin more werk for urself by moving them like that everyday unless u want to put them in flower then yea move them in the dark room for 12hrs. but i suggest u git a timer if u do put them in flower