What dosage of Corid did you use?
Have you check to see if there is any moldy feed, bedding, anything rotten they can get into, etc.?
If you have vet care, that would be best.
It's very hard to know what's going on with your flock. Looking quickly back at your postings you have treated for Cocci and worms. You also were losing chickens as well.
If you lose this one, I encourage you to send her for necropsy so you can hopefully get some clear answers.