I have three chickens and they have lived together about 9 months. Things have been going well, each hen laying an egg every day or so. In the last two weeks or so one hen has decided to bully one other hen. It's gotten so bad that the one being pecked hides in the coop most of the day. If I roust her out and put her in the run, the bully heads for her and pecks at her beak or rump. The victim hen has not laid in this time, although she sits in the box every day. No other factors like insects, vermin, nor changes in food, coop, water---nothing. The third hen is unaffected by either.