The babies will need to be fed at regular intervals around the clock - including night feedings, just like a human infant. Your vet can tell you how to mix a cereal for the babies. Keep them warm and clean and watch them for signs of distress.
First off, you need to have these birds on a good, healthy diet BEFORE you allow them to breed. This is important when babies arrive so the parents have healthy food to feed their babies and keep themselves nourished. when you clean the nesting box you should move them to a safe and warm place.