Question about Day 8 of incubation

I am currently trying my hand at incubating for the first time ever! I chose three eggs from my white bantam cochin/leghorn x hen (her mate is the same). I have candled every few days or so, and things seem to be right on target except for one egg. In two I can see the tiny embryo moving about, but I don't see an embryo in the third. I do see one large blood vessel that looks just like a ring around the entire width of the egg, and a few tiny branches off of it, and I can see the blood pulsating and moving through the vessels. The vessels in the other eggs are more random and scattered; in this one it looks like someone just drew a circle around the egg with a Sharpy (FYI I am using a LG still air with turner).

I guess my question is, is there an embryo in there and I just can't see it yet? Admittedly, my flashlight isn't the greatest, but I would think that after this long, I should be seeing an embryo. I have read the candling sticky a million times, but it's not really a help for my specific question.

When should I give up on this egg, or should I leave it for a while? Thanks!