We have a rooster and 4 hens. One of our hens is being pecked on by the others. They won't let her eat and she's acting sick even though she does eat. She stays off by herself in the yard and tonight they wouldn't let her on the roost. We've noticed she has white spots all over the top of her head. Any ideas as to what this is. She doesn't appear to have lost feathers. What do nits look like. I wonder if it could be lice.