One of my hens has an excessive amount of poop build-up on her butt. I noticed this a couple of days ago, but was hoping it would clear itself off. Well, it hasn't, and I'm wondering if she might need a little help. I was on the lookout for pasty butt when my girls were chicks, but I guess I just assumed that they didn't have this problem as adults. She is acting fine, and doesn't appear to be bothered by it, but I don't want the area to start festering. Should I be concerned about this, and how do I go about cleaning her up?