We filled our incubator with buff orps, silver laced Wyandottes, and australorps. Literally every egg hatched EXCEPT for any of the australorps. We candled and saw live babies in most of them. They just didn't hatch. These eggs are from our flock, and we use them for cooking and hatching and what not. We have noticed that the australorps give us a huge thick egg and sometimes they can be difficult to Crack open (for cooking) and alot of the times we have to actually tear the membrane in order to get the yolk out. They're almost like giant quail eggs. You can Crack them but they don't break open easily. Could this be a factor in them not hatching? Again, we candled and there were signs of life leading up to hatch day.