Factors for Infertile Eggs?

[T.Pierre5]

I recently bought hatching eggs from someone and 100% of their Black giant eggs were infertile. He has a 4 hen to 2 cock Ratio. When I told him about it he said I was the first person this ever happened to. He also incubates his eggs and told me that of the 96 eggs he set in his Bator only 34 hatched and 32 were alive so he said he figured something is wrong. I went by him last Saturday and he showed me a number of eggs he had thrown away and said he doesn't know what's going(I'm guessing infertility). He gave me some fresh eggs he picked up Friday which I collected Saturday and set them in my bator Sunday.
My question: What could be factors that are contributing to the infertility

 

[sourland]

Excessive feathering of birds, roosters not allowing one another to breed, poor health of birds - that's a high rooster to hen ratio.

 

[T.Pierre5]

his cages doesnt allow for the hens and roosters to have much movement and his hens and roosters are really huge.