I have two full grown hens , a naked neck and a gold phoenix, and recently purchased a new RIR pullet. She is about 7-8 weeks old and I have kept her seperated in a pen inside my coop. but when I let her out the other two gang up on her and peck at her nonstop. I have also taken one hen out so that it was a equal match, but this still doesn't help. How can I intorduce them without the others killing my new Pullet?