This has been going on for about 6 months. One hen will not lay for a long time, and during that time there looks to be yolk in her poop. When she resumes laying, the yolk disappears. She is currently pooping yolky, no eggs. Second hen has always had issues with being egg bound, but now only lays shellless eggs. The third, at barely a year old, my Buff O. stopped laying for about 3 months, and is now laying again. Yes, they have access to oyster shell. I've posted about this before and no one was helpful. I'm hoping the right eyes see it this time.