If it is Cocci, and your using Corrid, don't use any other vitamins or supplements because it will counteract the Corid. Corid is a Thiamin blocker, which is what feeds the intestinal parasite, so it essentially starves the parasite so it can't reproduce. Unfortunately, once the bloody stools appear, it can be too late. I learned this the hard way with my first batch of chicks a few months ago
Just keep them on the Corrid, cross your fingers, and hope for the best 

