My Gertie seems to get a dirty bum frequently. Feathers in her rump seem to clump together and collect dirt. I've cleaned it with warm water on occassion and found no signs of any other problems. She is a RIR, 8 mos old, lays very frequently, and has a rosy, though not red red comb, and I use DE in the nesting boxes and dust her as well. She is a real little workhorse who loves to scratch and dig all day long and doesn't seem to be lethargic in anyway. Any ideas what causes this? ...or what I should be looking for? Thanks all!