My cockatiel laid 3 eggs and 1 hatched after 21 days. It's been another 10 days still the remaining 2 eggs didn't hatch yet. But they are well fertile egg. Kindly suggest what should I do?

hi, i am finding my cockateil babies dying during hatching from eggs. 2/3 passed away this way and the last egg was not fertile. i may also mention that the cockateil laid 5-6 eggs about one month earlier that i had to waste because their place was in a new home (with same cage) and the female...