Having a separate dish of oyster shell available is always a good idea, even when feeding a layer feed. You are adding extras, which may alter the balanced nutrition in the layer feed.
She may only need more calcium and fewer treats!
Many high producing hens (and others!) develop fatal reproductive problems, sadly. I hope she's okay.
My youngest was a cute bantam purebred Ameraucana, who died at about six months of age,
never laying a single egg, and with peritonitis.
Mary