How old are they? And are they laying? Sorry, can't remember if I read that in your post or not. If they are not laying then block off the nesting boxes, allowing them to sleep in the boxes is just creating a nasty habit.
A 4x4 coop would be best for only 4 chickens, most recommend allowing for 4sq ft per bird inside the coop and 10sq ft per bird in the chicken run, so your chicken run (8x4) would be best for 3 birds. Do they free range? Over crowding can cause a lot of health issues and stress for the birds.