Mysterious death in new born chick

In 2009 breeding season and is my first season of breeding white-rumped shama, I encountered a few mysterious death in young chick that only hatched for few days (less than 4 days old).  I think because of the too many chicks in the nest at the same time (avg. of 5 chicks in the nest) cause the weakling to perish; thus the parents removed the dead one out of the nest.
In this 2010 season, right of the first clutch, I have one dead chick that approx. 2 days old.  I don't think the nest has more than 3 chicks inside (since I have no camera to view), so the theory of too many chicks compete to eat is not apply here.  From the picture below, it looks like the chick has digestion problem as the abdominal area is quite large compare to the body size.  Maybe it has problem of constipate? eating spoiled food? or just a weak one by nature.
Necropsy of the two days old chick could not find any concrete conclusion.  There is small amount of waste in the intestine.  The stomach is quite large with almost fully digest food inside.  One thing I notice is that there are lots of fluid inside.  Anyone has any idea/ explanation about this mysterious dead in young chick?