I am feeding the Pruina flock raiser. I give them grass and dirt after the first couple of days. All seem to be running properly. I suspect that the lack of vitamins in the food is helped by fresh grass. I also give an egg mashed up, or tuna, as treats. I have considered getting the yeast, but never used it when I had ducks before. I never fed them anything special back then, never heard of it. Just let them out on the lawn ASAP! Here, I am bringing the lawn to them.
Purina flock raiser does have more niacin than chick only feed so I think that helps.
My tiny chicks are a week old today.

On my to do list is setting up a small outdoor space for them to have some ground time during the heat of the day. Yes they will have sun/shade option as well as dirt/grass option. One BSL is noticeably smaller. I am calling her Tina. I think they could benefit from some ground time and real sunshine.