Our Cockatiels P-chan & Pebble Feeding Their Baby - 3 days old

Our pet cockatiel P-chan has laid a total of 13 eggs between July 27th and August 30th. The first 6 eggs were white and small in size while the last 7 were big and pinkish in color. None of the small eggs hatched while one of the big eggs was being stumbled on and damaged one night when the parents got scared of something in the middle of the night. Chick #1 was hatched on Sept 10th chirping all day but was found being left in a corner of the nestling box and chilled out to death the day after on Sept 11th