These were the best pics I could get, as I had to hold the chicken while my 4 year old shot pics with my cell phone :-( This morning I went out to feed the girls and I noticed 2 of our 4 BO's with dirty looking butts and bald spots under their vents. One is broody and I've been keeping her in a makeshift pen within the run during the day, but she's not one of the ones with the icky butt. Is this mites? I don't know what else it could be. I dusted their butts with DE when I found it, but I'm unsure what else to do. Does anyone with some experience know?