I was checking in on this thread because one of my hens has been laying soft/no shell eggs off and on and wanted to check to see if there was anything else I should do other than layer pellets (with calcium) and oyster shell. Decided just to share some winter experience - had a few "no shell" eggs over this past winter after the hens started laying again (they took a break between December and January as I don't add light). The weather was so cold I did not realize at first that they were no shell since the entire egg was frozen solid. It seems that the fall molt and winter darkness combined with extreme cold appeared to tax this poor hen's system. I didn't consider it a problem but did keep an eye on the issue to make sure it didn't continue. Never did find out who it was but suspect it might have been a silver laced wyandotte.