Hey,
I am hatching non-shipped Marans eggs every few days and they are harder to get out of those tough dark shells and if they pip and don't zip quick they get shrink wrapped easily but they are hatching at a very good rate. I think the quality of the lines is of utmost importance. They need occas help with zipping, but the chicks are hardy and vigerous. From my shipped eggs, some were obviously of better quality and hatched much better. Now, the birds are good indicators of why I had poor hatch rates. Look closely at the breeding is my thoughts. JMHO
ETA: I am sorry too, PM me.