If you really need to know more now, then you can 'candle' the eggs to see what's inside. It can be hard to do with quail eggs, but the general idea is that if you shine a bright enough light through the eggs, any that have been developing will be a shadowy blue/black color because the chick is inside. If you see movement, they're definitely alive, but if you don't then you still don't know whether they're dead or not. Any unfertilized eggs, or those that died very early on, will be a yellowish/transparent color when you shine a light through. You could discard or open any clear eggs to see what happened.
There is also another method called the 'water test', or 'float test'. You must check that your eggs don't have cracks in them though, else you could drown the chicks. Carefully place your eggs on the surface of 2 inches of warm water. If you see any noticeable movement of the eggs, then it suggests there is a live chick in there. If you don't, then you could still have a live chick in there.
If you get to the point where you feel like discarding your eggs, but aren't completely sure that they're dead, some people carefully make a hole in the wide end of the egg where the air sac should be, and start slowly opening the egg from there. If at any point you see movement, you can still put the egg back into the incubator and see whether the chick is strong enough to make it.
