My broody is due to hatch on June 15th. Right now she is with the rest of the flock, but I am going to isolate her with her eggs. Once they hatch, do I feed just starter feed alone or do I continue to put out Layena in addition to starter?
If I isolate at all, I do it only while they are setting, not after the hatch. Chicks grow up with the flock and remain accepted by the flock when the mama stops mothering them, usually around 4-5 weeks. Everyone gets the same food, either starter or grower. Oyster shell and grit are offered separately. Baby chicks can find small pieces in the grit dish and laying hens can take oyster shell as needed. No problem, and I rarely see a soft shelled egg, certainly no more often than when I fed layer feed. It can be pretty tricky to move a broody and there is a definite danger they will abandon the eggs entirely.
One thing you should be sure not to do is allow baby chicks any access to the Layena, or any layer feed. The extra calcium can damage organs, particularly kidneys, and possibly even kill them. I have never had a problem with baby chicks eating oyster shell, though. And a broody doesn't even need layer feed while setting or raising chicks as she's not laying eggs.