Well the wife candled them and only one looks to have veins.
The others have spots that look like the embryo, but if they have veins they are really small. We will have to re-candle in a couple of days and see if veins develop. Generally no veins after laying has historically meant they are not good.
I still wonder scientifically which of the pair is responsible for that kind of thing. I mean for an egg to come out looking nice full and white it had to get fertilized by the male since the slugs are eggs that never got fertilized. On the same not if it got fertilized by the male, but never developed into a viable offspring why would the egg fully develop around it since it was not viable early on?
So many questions, so little time.