Just keep an eye out for her. Is she just coming into lay after a molt? Does she have access to oyster shell? Just hoping it's an isolated incident. I agree it was likely a shell-less egg that broke inside.
Thanks for that, I've been feeding them Layena with calcium and have never supplemented with Oyster shell. I might get a couple soft shells a month out of flock. I have now decided to add a bin with the Oyster shell. My 7 hens will be 2 years old in June. The first winter, just when they started to lay, I had a light timer to keep the days longer for them and production was great. This year, I let nature take its course. I'm getting on average 3 per day right now, not sure if that's normal but they seem very healthy and happy.