FunClucks
Crowing
Many of us, when we talk about hatch rate, remove any unfertile eggs from our calculations. We remove "clears" after the first week, and then say X/Y eggs hatched. So if you set 12 eggs and 4 of them turn up clears (unfertile - no development by day 7), and you hatch 4 chicks and 2 survive, you would say you had 4/8 hatch and 2/8 survived. So you have a 50% hatch rate, which isn't horrid, and a 25% survival rate, which isn't great. I, too, am questioning your incubator.No they were from a friend. She had just had a great hatch rate of 11/12 a bit ago. Although, when I candled 4 of them weren’t even developed.
Clears, or unfertile eggs are either too old (as previous poster says) or were never fertilized, or damaged in shipping (not the case for you), so when you look at the success of the hatch, those are very different reasons than when something goes wrong as the chick is developing or hatching.
FYI, my favorite incubator is the Nurture Right 360. Great price point for the many features, and it's almost set it and forget it. Other folks have other favorites.