I have a Buff Orphington who has had some dirty tail feathers for a while now. She is only five months old and basically had them since shortly after they were first allowed outside. I have play sand in their run, but they have dug down to dirt in a few small spots. I have checked her feathers, the shaft and around her vent and it all seems very clean (no mites). I am paranoid about mites with so much talk about them. I use DE on a regualar basis in the coop and run since they have been outside. Since she is light in color I am guessing a few dirty feathers are more obvious. My Black Astrolorpes probably have the same thing. Does anyone else have chickens that just have dirty feathers without it being mites or any health problems??