I don't know ducks but thinking it maybe Niacin is ok since it could be a vitamin deficiency or it just could be a "genetic" issue. Sorry I can't be of more help. @DuckLady
You may want to search/post in the Forum for Ducks, may get more responses pertaining to ducklings.
You may want to search/post in the Forum for Ducks, may get more responses pertaining to ducklings.