Hello. I have six city hens, and they molted as normal in the autumn, but now two of them have lost large numbers of feathers. One has a completely bare neck and the other a large bald spot in the hollow behind the neck. I've looked for mites/lice by checking their faces (where I saw them the last time we had them) but didn't see any. What could be the cause of this? I have a video showing the feather loss, but I had trouble uploading it.