It is so hard to know what you are looking at with dark eggs as this was my first hatch and I did not have a clue even after reading a lot of things. So first, I would say to just check them each day. Mine looked difference most of the time from each other in some way. I couldn't see veins but maybe in 3 out of 8, 1 or 2 looked like there was not a good air space, something on 2 or 3 I would see the black area and thought that perhaps something happened and they would not hatch.... etc... my advise is just go with it, check each day with a very good candler and do it in a completely dark room. This is the only way to really see better. I even tried marking them and understanding what others where saying about the air space and truly it was not until the very last day or two that it made any sense to me. Enjoy the process and when you see them moving, that is when you will truly know, however even then I could not be sure with 2 of my eggs. Some move a lot and some do not. Yet they did all hatch... now I know what to look for! Again good luck!