One of my 6 month old Isa Browns has feathers missing. Is this a pest, disease or from another chicken pecking her? She is one of 4 that we introduced as babies to 4 other older Isa Browns. I thought they had all integrated but there is one that is still a bully and chases them away from food but I haven't noticed her pecking at her. If you know what this could be caused from your help would be appreciated as well as a remedy if there is one.