Also with ducks, please remember they require more niacin than chickens and less calcium. The niacin is extremely important for their feet and legs.
I mix my chicken feed except chick starter but the ducks I start on a 50/50 mix of unmedicated chick starter and unmedicated wild game bird and turkey starter. That is what was recommended to me by Holderreads when I purchased my ducklings.
Metzer is a waterfowl hatchery. They have a wealth of great information at their website which is Metzerfarms.com or just google Metzer. Under the Care and Management tab they have several pages you might be interested in, including a calculator that helps you calculate feed ratios to obtain the desired protein level.