I have 3 white chickens in the “special” chickens run. A silkie, and 2 polish or Sudan mixes (? I think, they are small like the silkies). For some reason, just the white ones here cannot stay clean… like they get mud (or maybe mud colored poop) on their booty and bottom of their legs daily. Not sure why… they are no more fluffy or feathery than the others in their apartment! They have a pretty large run and get to free range. Anyone have a remedy for this?