(Hello, I'm new on the forum, but I have been reading for a while.) Today, I noticed something built up on the feathers under my hen's vents. Closer examination showing that something was crawling on their feathers! I believe it's mites, but I don't know what to do to get rid of them! The feathers are caked with a grey something, and little red mites are everywhere under their vents. I don't think the mites have spread yet, but what do I do? I have heard about dusting them with something, but what should I do, and how do I go about it? What do I need to do to their house? Will it affect my chickens health? Any information would be great!! Please help!