Hens that are laying eggs need extra calcium for the egg shells. If they free range, they can get a lot of calcium from some of the things they forage on, certain plants, hard shelled bugs, even gravel they use as grit if it is made of limestone. Layer feed has a lot of calcium in it. Some chickens still need extra calcium for their egg shells. Oyster shell can provide that.
If your egg shells are hard, what you are doing is working and you don’t need to change anything. But if your egg shells are thin, you can offer oyster shell on the side. Or if you just want to, you can offer them oyster shell. They probably won’t eat much if they don’t need it.
Also, baby chicks should not eat layer feed because it has excess calcium in it. Many of us that have young chicks in the flock feed Grower, Flock Raiser, something that does not have a lot of calcium in it and offer oyster shell on the side for the hens that are laying eggs.