Sometimes they just die. A malpresentation is a crap shoot at best.
I had a chick do the same thing. It weakened I took a chance and did an emergency assisted hatch when it failed to zip. Thought he was a goner as he lost a lot of blood. Little devil lived and is now almost a year old.
Sometimes the dice roll in your favor sometimes they don't. You have 2 beautiful ducklings to celebrate with your class.
Are your kids old enough to understand what has happened?