One of my girls has a problem, she does thin-shelled eggs that are "not right". I hope it doesn't progress to something worse. I don't know which one it is, when I get my new run up and move the yard, I can try isolating them one at a time to find out which it is. (It isn't the one I put in with the new girls, I know that much).
(My isa browns are adopted, and I don't think they are the healthiest. I don't know whether they came from a battery farm or what, a couple have "strange" beaks and there's the one with the shell "issue" and they don't look all lush and gorgeous. I don't care, I love them anyway, I just hope nothing awful happens.)
What are the signs of egg binding or peritonitis? Is it dramatic, so I won't overlook it thinking everything is normal?
( pale around the face , wattles and comb ) . If you catch it early a warm float on a bath with some Epsom salts and massaging towards the vent , can help ' move things along '. Best to offer calcium carbonate on free take in the coop for those that require it .
Check the feed you are using for methionine and amino acids. Poultry require methionine to synthesis protein, so even if the protein levels are high in the feed the amino acids are crucial .