Question about what to feed my chicks and ducklings in the next weeks

Okay, up until now I have been feeding my chicks and ducklings Dumor, which I believe is the TSC brand, and my babies are thriving on it, ducks included. I know the chick starter is only for the first 6 weeks and after that I am suppose to switch them to grower/finisher. I checked the layer feed the last time I went to the store, as it was all that was available to look at, they were out of the grower/finisher, and the layer food is just for chickens. What am I suppose to move my ducks to? And if I find a different food to feed them, can I keep them in the same coop as my chickens when they get big enough? How do I do that without them eating one another's food? Owning ducks is new for me and I just want the best for all my feathered kids. My neighbors told me that chicken feed with antibiotics in it will kill my ducks, and I did read later on that it's bad for them and turkeys, but the Dumor doesn't have the antibiotics in it. It's affordable too, but is there a better brand I could be feeding them? What do other people feed their birds? And at what age do I start introducing fruits and veggies to my birds? I read in a thread that some people feed their chickens spaghetti and others give theirs oatmeal, etc. At what age can you start to offer them foods like that? Another neighbor of mine that has Golden Comets gives his adult birds table scraps, left over veggies from his garden, and halves of watermelons. I am planting watermelons so that I can offer some to my birds in a few months, and also because my 10 year old LOVES watermelon . Any advice I can get with this would be greatly appreciated. Thanks everyone.