While my last lot were hatching early this week, I found two of the bunch had very odd inner membranes The outer membrane by the shell was fine, not too dry or wet. Most hatched fine. However, inevitably a couple got stuck. When helping them out, I found the inner membrane, the one with the blood vessels, was thick and like jelly. The chicks were ready, yolks absorbed, blood drawn in, but they couldn't turn to zip. So, I chipped away the shell, and rolled back the thick jelly like inner membrane to pop them out. It was not like anything I have ever seen before. It was up to 2mm thick in places. Any ideas what caused this? Had a little trouble keeping humidity up until day 18 and got it perfect for hatching. They did start 2 days early although was running at just under 100F. Very confused!!