I have had chickens for a few years with no problems at all. Today I went to the coop to let the chickens out and they all seemed fine. Just now I went back down and one of my silkies is laying on its side close to death. I poked at it and moved it a little to see if anything had bitten it but it was fine. Then I saw black goop and white worm things on its bum. I think I may have read something about that before. Can anyone help?