Our chicks were given Purina SunFresh Start and Grow until they were 18 weeks old and we switched to layer feed.
We've used Purina SunFresh Layena crumbles and certified organic layer mash. Both are 16% protein. They cost about the same in our area, $9.90 for 50# for Layena and $10.50 for 50# of certified organic. We used the Layena crumbles, not pellets, because our flock would bill out the pellets and waste them. The organic mash is milled locally. It is more powdery, so we mix it with yogurt or buttermilk before feeding to our flock.
We picked these brands because they are both vegetarian feeds. I would rather not use any feed that uses animal proteins, as there are too many unknown possible problems - like BSE in cattle.
Layer feed shouldn't be fed to young birds, as the additional calcium can be hazardous to their health. We provide feed, grit and oyster shell 24/7 free choice. We feed organic veggies and fruits to our flock, but the layer mash is the main ingredient of their diet.