Quail eggs are very small and darker color than another eggs...
It's hard to see. For me I'm not candle them at all
Another thing u said u put 4 eggs in ....that's very
small amount....I put 30-42 eggs most the time
And 25 hatched from 42 , 15 hatched from 30 , or 18 from 30
So only 4 eggs...
Another way u can do ....check by floating test
Use warm water (100 F) and put the egg in there
If u see egg wiggering that mean it still alive and has hope
If the egg not move ...so u can throw away!!
That's the save way!!