Feed them chick starter/grower until they start to lay eggs... Once they start laying, you can continue using starter/grower with a side of oyster shells, switch to an 'all flock' with a side of oyster shells or switch to a layer feed, and even with the layer feed I recommend a side of oyster shells...
Unmedicated chick starter. Or if you want the medicated continue with that. It doesn't really matter if your only feeding chicks and adolescents. You stop the medicated usually around 8 weeks of age. I don't even use it. Unmedicated is about a dollar cheaper. There is also a grower blend but that usually cost the same and is simply less protein. I'd stick with the starter feed as 18-20% protein is a good mix for growing birds. The gig about the medicated is you don't feed it to layers because your eating the eggs. Other than that it doesn't really mater. So if you can't find unmedicated at your local store then put them on grower when they are late teens (in weeks) of age then change to layer when that bag runs out.