I have a BO who lays a soft shelled egg probably 4 days out of 7. Like you, I love her to pieces, and so far I've been lucky that she usually lays them from the roost and not in the nest. The other girls have not shown an interest in her eggs either, which I'm thankful for.
I feed layers pellets and also provide extra shell grit for my chickens. On top of this I bought a powder which is high in Calcium and Vitamin D, and is mixed into their pellets. They just eat it willingly. I have a liquid calcium on hand at the moment too, designed for cage birds such as parrots which my vet advised would be fine to try also. It is added to drinking water, and whilst I haven't used it yet, it is an option for later on.
I am hoping one or a combination of these things will help rectify our problem BO!
I am a first time chicken owner and got 6 hens and one rooster in my original flock. So far we have added one chick of unknown sex (he/she is only a week old) and I have a batch of 8 eggs under a second broody on Day 10. Like you, I wanted my girls to live long and healthy lives with me, no matter what happens egg-wise. I shudder when I think about culling - but accept that if one was suffering I would do what's best for them. I wish you all the best in your decision.
- Krista