What is wrong with my snakes eggs?

I have some problems with some of my corn snake clutches and was wondering if someone could help.

This is what happened leading up to the problem.
1) first the females would not 'sit' on their eggs.
2) second the eggs would be fine in the incubator for the first month.
3) third all but two eggs would die after one month in the incubator.
4) one of the remaning eggs would die 15-10 before the hatch date.
5) the last egg would either be extremely under size, or live on to be very helthy.

The clutch sizes where 7-15 eggs.
Has this happened to anyone before? Does some one know what went wrong?
Thanks!~Brooke

Likely causes, for failing eggs, are as follows:

1. Incubation temps were incorrect (i.e. too hot).
2. Not enough humidity during the entire course of incubation.
3. Incubation substrate too wet &/or too much condensation forming, on tub lid, then dripping on eggs.
4. Incubation substrate containing chemicals.
5. Complete, total/absolute, lack of any oxygen for entire incubation period.
6. The eggs, that went bad, were infertile.

....

Brooke, could you post a pic of your incubating set-up?

Pasodama nailed all of that. Your incubation methods have to be dialed in perfect. I would recommend just copying a successful breeder, if there's no info and it's a speciality animal, I bet you could email someone who's had them and bred them and ask.

Also temps should be constant the whole time, and the higher the temps the more problems you'll run into. For example people breed leopard geckos at higher temps to produce males I'm pretty sure, and that produces a lot of problems incubating the eggs and also resulting in deformities sometimes since a shift in high temperatures could be super detrimental.