My Barred Rock, Maude, is a very perky fun chicken who lays an egg a day. She eats well, forages well and drinks. However, her butt is always dirty. I clean it and then it's dirty again. She poops normally but obviously sometimes not. Her eggs are perfect and she comes running when I go inside the chicken yard. What the heck? How can I fix this or do I just keep washing her butt or do I just let her live the way she is? Are some chickens just dirtier?