Hello, my baby duck just started walking on it's elbows in a wobbly sort of way. I've read this could be a niacin deficiency in their diet. They have only had mashed chicken feed pellets since they hatched. So I guess that's what it is. They are 3 wks old, how is the best way to treat this and what is the best pellet food to feed them from now on. Also I've heard to use brewer's yeast, where do you get that and how do you give it to them? Thanks so much!