I have a 1 year old hen that has just in the last 3 weeks started staying in the coop, not brooding, she eats and drinks and moves around. If I take her to join the others she scratches and pokes around a while and lets the rooster at her but she will eventually go back in and stay until I take her out again. I have taken her to the vet that has chickens and specializes in birds, the vet says other than a grade 1 parasite and lice problem she is very healthy. I have washed her butt with cool water with a drop of doterra onguard, as she has some waste stuck to her and then coated her back end with diatomaceous earth. I feed organically and add a liquid mineral to their water and sometimes a little vinegar. Any idea what her problem could be?