We've had similar problems with soft shelled eggs in our flock and were told we have bad calcium deficiency even though we let them have oyster shells free choice. Here's what we've done: in addition to the oyster shells try feeding them kale, dandelion leaves, and collards. They're all really good in calcium and my girls love it all. I just have started them on it and we already notice that the shells seem to be getting harder.
The good thing about dandelion leaves too is they're free. Lol.
The good thing about dandelion leaves too is they're free. Lol.