You can feed Flock Raiser (20% protein) to everyone and oyster shell on the side for the layers. Or unmedicated chick starter. Or grower.
I would throw them some scratch too (the teenager chickens) to prevent reproductive problems...best to not spend the teenage months on 20% protein I have read...17% is better. So you can just toss some scratch out for them too to kind of lower that protein if you go with the higher protein feed for everyone.
So, in essence, it would be the BEST to feed everyone the grower feed, which is perfect for the little ones, and give oyster shell on the side for the layers. Then you woudn't need to be tossing scratch out to lower the protein.
If your eggshells get soft then you can mix in the oyster shell...flemingoutdoors.com has a recommendation for amount on their sale page for oyster shell if you need to do this. I have to mix my oystershell in as I make my own layer feed basically or the eggshells get soft in my flock.