I agree on giving liquid BComplex along with the other recommendations. B complex is amazing. Sure hope it will help your baby. The dose is 1ml over a small amount of special treat daily until up and walking and then for a week more.
Here is info https://www.backyardchickens.com/threads/niacin-deficiency-in-waterfowl.1367557/
Here is info https://www.backyardchickens.com/threads/niacin-deficiency-in-waterfowl.1367557/