I've raised chickens for 22 years, and I've never experienced anything like this. I noticed an unusual looking dropping yesterday morning 4/3, by the end of the day yesterday they were defecating pure blood, but acting ok. I put them on Corid water and electrolytes. By this morning 5 are dead. These chicks are 3weeks old today. And they just finished a Corid treatment less than a week ago. I just pulled another group of chicks through this, they are about two weeks older. I almost lost them around the same age but pulled them through by tubing Corid 2x a day for 4days. They havent come in contact with any other chicken that has coccidia. I've never seen coccidia act like this before, it seems exceptionally deadly. It did not respond at all to Sulmet, which I've always used. What's going on?? Any thoughts?