We have 8 hens that are about 2 years old now. They were raised together and got along well. They have a 20 x 20 coop which they sleep in at night and free range all day. One of the hens, a red sex linked, has spurs and some of the hens pick on her. One will jump on her back and peck at her head, Some pull her feathers out and chase her around. We just got a rooster hoping that will help, however he is only 3 months old and is just getting used to everything. Any ideas what the problem could be? Thank you.