Half of my 10 chickens have a strange diaper like rash on their bottoms. At first, I was thinking this was just a result of molting over winter...but half of my hens never regained feathers on their bottoms and have this horrible rash. When I touch their bottoms, the area seems hot. Has anyone ever encountered anything like this? Please share your suggestions for dealing with a bad rash on a chickens bottom. The rash area is about the size of softball. Hens are about 16 months old.