I hang my feeders and waters from the ceiling for the purpose of allowing a bird to be able to 'duck' under them to get away, that is often all that is needed in my coop. I also have a few of those old milk crates, I place them around the coop floor for a way or place to get out of sight. Silly things… Also I have at times used a creep, what I mean by this is a place that the smaller birds can get into, but the older/bigger bird can not so easy. Creeps for farm animals are used to allow the young stock access to free choice grain, pellets and the like. But the principal in the coop is much the same. A hole cut in a piece of wood and a pallet or such making a protective wall, it need not be fancy, just something to give them a break from being harassed non stop. Also if it is one or two birds doing the chasing, a day or two in time out can make a difference as well. Place them in a dog cage/crate or such and let everyone else work things out, when the offenders go back in… it is they who need to reassert their position in the flock.
Best to you and your birds,
RJ