Babies, babies, where are they??

Well, Darwin and Etcetera are a pair of my cockatiels, they've had babies before, and they're having them now. They laid seven eggs, and I knew all seven wouldn't hatch, but the first one didn't hatch! I would think that if ANY of them were to hatch, it would at least be number one. The second one hatched Tuesday, and now it's Thursday, and I should have another baby, and I don't. It would really, really suck if I only get one baby out of seven eggs. I knew I should have tossed egg #7. I've got the heat going in the bird room constantly which is probably going to up my electricity bill by $50, all to get one lousy baby? I think if they only hatch out one I'll just not handfeed it, it can be parent raised. It's just not worth the effort.