Have ten 7-month old hens. Someone has stool that is dark in color and runny. Can't figure out who is the owner of it, but all hens are doing well, eating, running around, etc..... Any thoughts on how to treat the owner of the stool, as well as if it is best to treat all. If so, what should I use, how to administer it to one/all of them. Thanks for any suggestions.