Try extra feedings of finely minced hard boiled egg and crumbled tofu. These are both high protein foods that are easy for a chick with special needs to digest.
It appears one leg is weaker than the other. So that's why hobbling alone wasn't enough. I would make a little chick chair and use that and the hobble several times a day for short periods. https://www.backyardchickens.com/threads/versions-of-chick-chairs-please.1166308/
Chick chairs help keep...