I have 3 hens, 2 blue slate and a wild, one tom. They lay out by the fence, forget about fake eggs in the coop to tempt them to lay where they are "SUPPOSED"to, it didn't work. For 2 days now, somebody has been laying an eggs that the shell is like rubber. I don't know who's doing it, but............... I feed them very well, and they always have access to oyster shell, and they get egg shells too. The other eggs are so hard that they are diffucult to crack for breakfast. What am I doing wrong?? THANKS for the help, in advance!!