Hi, welcome to BYC!
As long as there is oyster shell available they will be fine on their current feed.
Yes your boys can eat layer, but I don't feed it to mine as I have read studies showing that extra calcium fed long term to non laying birds such as chicks, roosters, or molting hens *can* (doesn't mean will) suffer from gout or even kidney failure. For that reason, in addition to hatching and having chicks in my flock most of the time.. I use a flock raiser which is 20% protein and 1% calcium with OS on the side for layers. Yes, sometimes I see a chick or boy picking at the calcium but they can mostly avoid it verses being mixed in the feed.
Also, 16% protein in layer is the bare minimum needed to sustain a light bodied layer like a Leghorn. But heavier breeds like Barred Rock do better on more protein. It's the amino acids really. I also read studies showing better hatch rates and chick viability when hens given more protein, which to me says better nutrition for my family. Also, many people who show their birds know that feathers are made of 90% protein and so feed higher protein because they get better, fuller, shinier feathers. My only point is if you choose to feed layer, make sure not to diminish your protein with treats like corn and such.
Since you do have the oyster shell out already, note that sometimes a soft shelled egg happens as a standard hiccup and does not mean your girls are lacking calcium.
Oh, and congrats on your first egg!
