Run space. (Not coop space.) Even though they don't free range, they need room to dust bathe, run around, get away from the bullies, practice flying, preen, stretch, sunbathe, scratch in the dirt, etc.
I now have 9 chickens in a 400 square foot run, and I wish I had more space for them! I can't free-range either or they would be coyote food.
I don't know how you tell you have to little space, any thoughts on that would be appreciated. I was in the run today to feed them, and there were many dust bathing. I didn't see anyone doing stuff I would consider weird, but maybe I should be looking for other actions??