I would remove all toys and feed them separately. Maybe take them for long walks and tire them out a little? I don't know where you are located but it has been a long cold winter for alot of us and more than a few bullies are getting cabin fever. Keep an eye on body language. Any staring, or rigid body language is no good and you must immediately redirect them. Have they had complete physicals? Maybe one of them isn't feeling well and is cranky?? Start out trying these changes, if nothing works, I would call in a behaviorist. Good luck. Don't make any decisions about rehoming anyone until we have tried everything. We are all here for you. Good luck keep us posted.