It has been proven in Poultry that....when fed a high diet of fats and proteins......that the embryos die full term in the eggs.
The respiratory system is one of the last things to develop and because of the types of nutrition intake...causes the respiratory system to fail at the last stages of it's development.
Reptiles and birds are very similar in make up.

What species do we see this happening with the most in captivity? Mostly reptile eaters...such as BHPs, Womas...(and lizard eaters... such as the Anthills).

Change the diet of the adults (off of the rodents)....get better hatch rates.
It worked for me....with my BHPs.

Ironically....the only animals I have any problems hatching....are the ones from adults... that will only eat rodents.

Cheers,
D.