We have some groups of chicks that are a few weeks old. One hen has three chicks - two Standard-size, and one bantam-size. The bantam, which was fine before, has been acting very weak. Unfortunately because of the normal size difference I can't compare the chicks to determine whether she's growing or not, but it appears that she is a lot smaller than the others.
She can't hop up the steps that the others can easily fly up. She peeps constantly and seems to be really tired.
Also, I'm finding bloody poops in their area. They have not been getting any medication and they've been being fed layer food.
I know, I know. Shame on us. We're going to feed them chick food now, though. But we never give our chicks medicated feed. Is that okay? Is there anything that can be done? I know that this probably means Cocci virus, and I'm really scared. I heard that it stays in the ground forever, so the other chickens (which walk around where the chicks are) could easily get it.
What should we do? Would it be better to put the chick out of its misery? And how should we treat the Cocci?
She can't hop up the steps that the others can easily fly up. She peeps constantly and seems to be really tired.
Also, I'm finding bloody poops in their area. They have not been getting any medication and they've been being fed layer food.

What should we do? Would it be better to put the chick out of its misery? And how should we treat the Cocci?