You're probably going to have to make two flocks. There's way too many drakes. and they'll end up terrorizing the females. I feed Mazuri Waterfowl feeds because I can order them from Chewy and have them delivered. Till the females start laying eggs, you should be able to feed them the Mazuri Waterfowl MAINTENANCE diet (
https://www.chewy.com/mazuri-waterfowl-maintenance-duck/dp/248786 )and have free choice grit for all of them. The boys will always stay on it. (Somebody correct me if I'm wrong because It's my first year with ducks LOL Once the females start laying, the females need to be switched to Mazuri Waterfowl BREEDER diet (
https://www.chewy.com/mazuri-waterfowl-breeder-duck-geese/dp/248789 ), which is much higher in Calcium and have both grit and Oyster Shell available. I like the Mazuri because it floats, so mine eat it as soon as I put it into their water. I've tried the Kalmbach Feeds but my ducks seem to grind it up and leave me lots of powder, and not eat it.
My understanding is that the feed is made so you can give up to 10% of their feed in other items, and they should still get a balanced diet. My Runners love watermelon, bananas, green beans, peas, Spring Mix lettuce cut up, Black Soldier Fly Larva (also on Chewy and high in Protien and Calcium for when they molt or are laying eggs), cut up ripe tomatoes, green peppers, etc. Some people feed minnows and earth worms, but I'm concerned because both are intermediate hosts for parasites, so we don't feed them. I'm sure eventually they will get earthworms by themselves LOL