Never mind about those questions, I did some research

. I have a more important one than those ones, honestly. The middle egg is developing (it's Day Six now, it started yesterday). It has an eye, and a few veins. But the body seems to be a curve, and I'm worried it's one of the curves in eggs that signals the chick is dead

. And it didn't move (I don't think). Should that worry me?
Also, in the other two I just see a yolk. Should that worry me? Should they have started developing? How long should I give them before replacing them? I REALLY don't want to replace them, but since I don't want to wind up with a single chick for the third time (Dawnwing got some friends, but unfortunately, with Marshy we didn't even think of it) I might have to. And I'd want to know when so that Russetwing won't need to be alone for too long.
Thanks! Please answer soon, I'm worried about the two undeveloped eggs, and really worried about the developing one.