Feeds are generally formulated for different parts of a birds life. Such as starter (generally about 20% protein, 1% calcium), grower / maintenance (14 to 18% protein, 1% calcium), and layer (16ish% protein, 3% calcium). The name on the bag of feed let's you know what stage of life it's intended for.
Some brands of feed lower the protein level of their starter so they can just make a starter that you can feed until it's time to switch to layer.
Some decide to feed an all flock instead of layer. I've tried that, and while it works for many, it did not always work for some my birds. Had some birds that had no idea the oyster shell was their calcium supply. They layed soft shell and supper thin shelled eggs.
Not knocking that feeding style, it just didn't work out for me.
Also if you have waterfowl coming in, I highly recommend supplementing Niacin. The easiest way I have found is to mix BVS chick vitamins in their water. One half teaspoon makes 3 gallons of water.
https://www.qcsupply.com/549992-bvs...rm8L_e3OFTRutr9TUyIBb1CakoqYFjtBoCdLQQAvD_BwE