Thank you so much for the great info, and how scary, hope I don’t run in to this with my girls, yikes. It helped me to rule this out as the cause of my young Isa brown abruptly stopping laying at 22 weeks age. She has been laying one a day since 16 weeks with no issues, she’s acting normal, eating, drinking, happy. I feed ADM layer crumbles so am going to add oyster shells, although all 3 girls have had perfect shells since starting. This girl had one membrane egg a few days after stopping and none since. Am perplexed. They’re cuties so will just be a pet if she doesn’t restart laying 
Really appreciate all the info!
Really appreciate all the info!