Yes get the niacin and add it to their water, I think you'll notice the difference in a couple of days.As far as I can tell, she's still falling far enough to end up on her back. I took her outside yesterday and saw her do it a couple times outside. However, she's not managed to get herself quite as dirty today. Probably because they haven't made as much of a mess in their brooder box today.
I have been seriously considering getting some Niacin pills to give to them, in addition to the Brewer's Yeast. The pills I would get are from Wal-Mart and are 500mg pills. I was thinking I'd break the pill open and add it to their water. That way, I know she'd be getting enough Niacin, even if they spill half of their water. With the Brewer's Yeast having only .55mg (yes, that is just more than half a milligram) per pill, I am not sure she's getting as much as she needs. Do you think adding Niacin is a bad idea? a good idea? I read that ducks need more than 10mg per day, and I'm guessing that a goose needs more than that. What do you think?