Since you have 2 or 3? laying adults you might want to get some calcium citrate tablets and just feed those directly to the birds. Minimal time commitment and guarantees they get a calcium boost.I think it's a low-calcium thing but I'm kind of at my wit's end with this. They REFUSE oyster shells. I am getting no eggs now so I can no longer crush up eggs shells and feed them back. I have a lot going on in my life that I don't really want to get into, and all this management with my flock right now is adding a lot of stress on top of that. I'm extremely frustrated.
https://www.backyardchickens.com/threads/soft-damaged-eggs.1452762/#post-24179334