have to agree with Dipsy doodle on this one.
The medicated feed thing is an old myth, they would have to eat their body weight 2-3 times over per day to have any trouble from it. I have fed medicated feed to all my starting waterfowl over 27 years of keeping them, everything from domestics to near 100 species of migratory waterfowl, never once had an issue with it, and never had one get cocci either.
Also the niacin thing is pretty rare in waterfowl. Yes it's true they need more than chickens for sure, but there is niacin in most all chick starters. They only need 60 parts per million so it doesnt take much, most all feeds have this bare min amount in their feeds, therefore you rarely see trouble with leg problems from niacin deficiencies from store bought rations. Big problem from niacin is from those that feed solely corn or similar diets to their young birds.
So any starter in most all cases is fine, doesnt have to be one brand over another. Big thing is to watch the protein levels from 2-6 weeks of age as well as the carbs, calcium and magnesium to prevent the risk of angel wing. Keep the first 2 as low as possible and the last two as high as possible.
If you do notice a rare bird developing leg problems, add a higher niacin food source to the diet to correct it but these are very few and far between, personally, I have never had an issue with it.
Brewer's yeast is one good supplement that can be added, or you can just go to the health store and get niacin tablets and add to the drinking water for them.
In short, for waterfowl, most any feed can safely be used now a days, but yes, cheaper always is a plus for me as well with the economy like it is. Just dont cut quality for price.