Chicks and ducks together... question about niacin

[Back on the Farm]

I have my two week old chicks in the same brooder with my 5-7 day old ducks (they get along great). I've read that the ducks need niacin in the water to help avoid leg issues. Can I add niacin to the water for the ducks or will it hurt the chicks?
I've read/heard that people have raised ducks and chicks together successfully, but I'm wondering about the water with niacin.

Thanks
One of my two babies