What about in chickens that had previously been good layers with nice strong normal shells? The chicken in question is almost 2 and started laying thin shelled eggs, then soft shelled and now there is evidence of no shell, unless she ate the membranes. Last week I gave her cheese and her egg was almost normal again but still on the thin side, but then it went back to soft shells, then no shells. So I've discontinued the cheese and today tried a calcium citrate.If no membrane, it's more than a shelling issue.
Not sure there's a 'fix'.
Some birds are just duds.