Clipping may help, i've done that with young ones that all of a sudden just turned on each other... They did grow out of it over time and stopped bullying. I have used the "snap on blinders ", the ones that don't need a tool, on a very aggressive male once. I don't care for blinders, but in this case it was needed. ( I suppose it's like people with nose piercings, except birds already have a hole... LOL.... but I'm a wuss anyhow) If neither work, you may have to separate them if you can and they are getting a beating. If possible put them in a cage/pen next to the others so they can still see each other, but not hurt each other until they settle down.... Best Wishes.