I have three 2 week old chicks. WE went away for 3 days and my neighbors watched the girls. When we came back one I noticed that in the straw there was some dark stool, like black, not spotty just all black. The chickens seem fine, but I heard that this could be a sign of coccidiosis. Do you think my chickens have this? What should I do to treat it? Can I just give them vinegar once they already have it? Please help!