You can't really tell until they've been incubated a while. How long have they been in the incubator?
After 4 days whilst candling you should be able to faintly see a small dark dot with some veins emanating out from it
After 7 days this can be seen clearly with a wide network of veins coming from it even if you couldn't see it before
After 10 days the veins cover most of the inside of the egg, it looks quite dark in there, but some veins are still clearly seen.
I wouldn't throw away any eggs unless they are still completely clear at 10 days, or have a blood ring.
The chipped egg would probably have got bacteria in it, but again, I would have checked it for life first.