rotten eggs

[turtleluv88]

One of my eggs that I know was fertile because of the blood vessels inside and I'm sure I seen movement has now begun to appear rotten. The eggs are 62 days old and I noticed some little bugs crawling on this egg and then I seen the side of it collapsing. There is a dark mass inside but no movement. I started to smell some odor coming from it. All the other eggs have lots of movement inside them.

Any idea why the egg would just stop developing and the embryo die?