Right. They were fertile but then died. Which can happen for a number of reasons. The pics here are perfect examples. You won't see any healthy veins in the middle of this ring. It's caused from the blood pulling on the outer edges of where the embryo was growing and developing. Also, you may spot a dark mass (the deceased embryo) which floats. You won't see movement unless you move the egg. If you're never sure, wait another day or two and candle again. Once you've come across this several times, you'll begin to easily recognize which have quit developing. I can now almost tell right away if an egg is viable or not by how it looks upon candling.
Healthy/growing embryos will have nice veins and you may possibly see movement if they're far enough along. (Use a bright candling light. I use a big mag light and it works perfectly.)