If they were set on the same day, the dark mass is a good sign! Keep an eye out on the clear looking one. It might not be fertile so you don't want it to blow up on you.
Good luck. For future notice, it is best not to set the first eggs your hens lay because they are small and the chick may run out of energy before making it. All the nutrition they have to live on for 21 days is in that egg, and if a large bird is to come out of it... it needs more food. Not...