we got 6 ducklings at our local farm store 3 weeks ago. Boy did I get myself into something! But I love them and we’re working on getting their permanent shelter finished. Problem is 1 of 6 is not doing well. Seems to have a niacin deficiency. I have been adding brewers yeast to their feed for the past 2 weeks or so because I didn’t know about it at first. Even the people at TSC couldn’t tell me whether I really needed it or not. Anyone know if 1 of the 6 can be deficient and not the rest? Should I put additional niacin in their water or do something different?