One of my RIR hens has had a poopy butt. It seemed to take several days to build up to a 'clump' that had to be removed. It doesn't seem to bother her, she eats, drinks, acts normal in everyway...just has doody on her booty! So I washed it off, she was good for several days, then it started over again. So...again, I washed her butt (she doesn't mind at all, sits still while I do it), but now she is building back up again, and I noticed another couple of hens are getting poopy butts, too! I usually free range my birds most of the day, and I just wondered if it could be something they are eating? I decided to keep them all in the run for a couple of days, but not really seeing an improvement. I have never wormed or medicated my chickens in any way, just layer feed, oyster shell, ACV in their water, and sometimes I give treats of scratch or leftover cornbread, vegetables, cottage cheese with ground up egg shells in it, but nothing spoiled or molded...any ideas?