There is always a good reason for baby birds to die.Did they Kill their babies or did they die?,Breeding birds such as yours need to have Green food supplements when feeding young, the best way to get this is to soak some of their seed in warm water overnight , drain rinse, place somewhere warm till it sprouts 2-3 days rinse and feed to the adults, to get you started try feeding small portions of Broccoli.

As for hand feeding baby Zebras this is a task I would never take on it is not s easy as one may think.

You could always visit this site "breeding zebra finches"

Avian Care Consultant and Ex breeder

Hi, I have a mated pair of Zebra Finches that have laid eggs again. I got them Jan. 30th 2014 and their babies hatched March 6th. They did end up killing their 4 babies. So if their new eggs hatch I want to hand feed all of the babies. I need to know what to do. When do I start hand feeding them? How often do they need to be fed? This is my first time hand feeding baby birds. Thanks. (: