I became concerned with my chickens because our wild birds are suddenly dying with no injuries. This concern made me look at my chickens and I found mites possibly, they are the size of ticks and yellow, only seen around the vent. If they are not mites what are they? How do I fix or treat this? Only one of my chickens has diarrhea and is balding on her rump, the others have "clumped feathers" next to the vent with no other issue. Thank you!