I don't know if it was the same thing, and I'm a newbie to hatching, but my first hatch out of my own chicken eggs I had 3 or 4 that developed dark specking toward the end and in a ring around the egg, almost looked like something seeping thru. they passed the sniff test and I left them in because they were the blue/green EE shell that I had a hard time candleing thru. They ended up hatching. The one that was the dud and didn't hatch had looked fine. If they sniff okay, I'd be tempted to leave them, but then again, I've never had an egg blow up on me. Sounds traumatic!