About a week ago, we lost 2 8-12 week old birds (barnevelder, partridge pennedesenca, cuckoo marans, easter eggers). Since then, we have lost a bird or two about every other day. I don't see any diarrhea, but they appear dehydrated, then they get lethargic, then go to sleep and die. I know chickens don't vomit, but one of them urped up some clear fluid. We have coccidia medicine in their water. Anyone have any ideas?