I have 6 hens, 3 bard rock, 3 buff orpingtons all about 18 months old. They have all gotten along until a few days ago. One of the bards is just coming out of a molt and the other day when I let them out to free range for a bit, she refused to go back into the coop. I picked her up and put her in, but I noticed that she ran around like she was afraid of the others. She doesn't have any marks on her body to make me think that she is getting picked on, but when she is around the other 5 she runs like she is afraid and sometimes one of them chases her. Today I noticed one of the hens actually pecking at her. I have her separated right now, but I'm just wondering what would cause this behavior?