I am house and chicken sitting for a couple in Minnesota. The 25 chickens are doing well. I noticed about a week ago that the one lone rooster looks as if he is being picked on. His tail feathers are almost completely gone. I have been keeping a close eye on him and applied pinetar to his back, per owner request. It now looks as if it is getting worse further up his back and now onto one wing. His wing looks as if there is an open sore. I am unsure if the chickens are just going further up because of the pinetar on his lower back or if there is something else wrong. Can anyone help me?