failing to thrive

Hey I have a chick she's about 6 weeks old and just finished a round of Albon 5% oral suspension for coccidia. Now she seems listless and off balance. Her brothers and sisters are fine. I suspect a vitamin deficiency, though an online vet suggested possible overdose. Could I get some advice on...

This isn’t an emergency post, it is more for others who want to see what this looks like on a chicken. I finally have confirmation and just wanted to share. She (12 week old Lav Orpington) presented with one leg out in front of her and unable to walk on it and was very thin. As you can imagine...