I'm not sure of the difference. I have 2 hens (out of 31) that have lost feathers on their backside. I picked them up and couldn't see any mites, or anything. I'm not sure what I'm looking for. The skin is red/dry/cracked, and some feathers appear as if they have broken off. Is this from an agressive roo (I have 3) or is there another problem? I didn't know why it would be only 2 hens instead of all if it were the roos. Thanks!