One of my ten rescue chickens has a severely bald, red, mucky, faeces covered bottom. She appears quite well in all other ways, eating well, laying and running about the enclosure all day foraging. She is a little small and perhaps skinny but quite strong when I pick her up. I washed her back end a few weeks ago thinking that her general health would improve as have the rest of them. I have not wormed them yet as the stuff I need, is currently unavailable in UK , (manufacturing delay), and all the rest have grown back fluffy bottoms and look a lot healthier than they did, but we have been having terrible weather conditions with torrential rain and sleet and snow so I am surprised at how well they have been in view of the state in which they arrived. So any ideas folks?