I assume the Corid is in the water, right? I think if there is anything you can administer that treats mites and is not in the water, then it cannot hurt. So long as it dies not interfere with the Corid. When out of the coop, it I might spray the coop for mites. Maybe use DE or poultry powder in...
Yeah...hmmm.....like Nendei says - it could be coccidia as well... i forgot about it as my chickens were vaccinated against it and I have been moving their coops a lot. I would stick with the Corid that Nendei recommends and watch for signs of improvement...is there an avian vet nearby that...
Sounds like they may be anemic. This would be mites or worms or both. Fi d out what yiur local feed store has for treating it. I am just now getting back i to chickens after 30 years off from it so I know what ailments they get but don't remember the meds. Sorry...