I'm so sorry for your loss. 
A necropsy is the best way to know what happened for sure.
There is a diagnostic lab on this list in NH: http://www.metzerfarms.com/PoultryLabs.cfm

A necropsy is the best way to know what happened for sure.
There is a diagnostic lab on this list in NH: http://www.metzerfarms.com/PoultryLabs.cfm