So you want to have 4 different kinds of birds in the same pen, but the right bag of food is too expensive for you . . .
I use gamebird myself, but its one of the more expensive bags in my store.
I feed all my birds the stages of gamebird.
There is nothing wrong with being frugal, and I have no problem trying to save a buck or 10 on things like supplies or coop building materials, but if I couldnt afford/wasnt willing to pay for the appropriate food for my animals, I wouldnt have them.
HTH
Edit to add-
The start and grow you are using, at 18%, does not have enough protein for 3/4 kinds of birds you are keeping . . .
All the ducks, guinies, and turkeys should be on startrena(30%), which is the gamebird starter from purina, who makes the startngrow.
Those kinds of birds need the higher protein.