Yes that is the yolk you are seeing there. At this stage there doesn't look to be development in the first eggs pictured, but sometimes broodies don't sit diligently enough initially and that can slow down development, or some eggs get more attention and rotation under her warmest spots, while others get neglected, especially if this is her first time being a mother hen. Do you see definite development in other eggs? If they still look like that at day 10 then it's likely they aren't going to develop.
With the last egg is there sort of one stripe of red? That sounds more like a blood ring (it does fade after a few days from a ring to just a strip, and the less developed the embryo is the smaller the blood ring is overall). I'd leave it under your broody and candle again on day 10. If there's a significant difference between the eggs that are developing and these 3 then you'll know these ones aren't any good. But don't remove them until you are sure.
Good luck with the hatch.