How did their navels look after hatching? If you're still in Illinois, you could contact these people and see about having a necropsy done.
http://www.agr.state.il.us/AnimalHW/labs/
http://vetmed.illinois.edu/vdl/
-Kathy
http://www.agr.state.il.us/AnimalHW/labs/
http://vetmed.illinois.edu/vdl/
-Kathy