Weird poop

[Chicktori]

1 1/2 week old chick had this poop before it died also attached a pic of its belly hopefully someone can tell me what’s going on his breast bone seems to be sticking out and the belly under neath is almost mushy like

 

[Eggcessive]

It might have had mushy chicken disease, also called omphalitis, from a bacterial infection of the navel. Here is a good link to read, and there are pictures in the upper right side to click on:
http://www.poultrydvm.com/condition/chick-yolk-sac-infection-omphalitis