Have have 4 hens that have been together since chicks 10 months ago. Beginning a few days ago 3 hens are separating one from the flock. The 3 will all go over to a corner of the pen and huddle with their backs to her. It appears they are on top of each other. If the odd one out comes near they will run and chase her off. She has been flying on top of the coop to get away or today she was in the coop on the roost bar. HELP they have always been fine together!!