Sudden and unexpected death of our chinese water dragon

Question
Our seemingly healthy chinese water dragon suddenly passed away and we are trying to figure out why. She was acting normal, swimming a couple of minutes before. She then hauled herself onto her basking spot and (what we thought was taking a snooze). She then threw up a reddish substance and died immediately after. Her airway did not seem to be blocked with remnant vomit.  We barely had time to call the vet before she was gone. Is this something that you have heard of before? She was eating regularly and very active before her death. Thank you for any insite on what this may have been.

Answer
 I am very sorry about the loss of your water dragon.  The only real way to find out what happened to her is to have a necropsy done at the vet's.
 My vet had taken in a water dragon as a rescue, the poor thing already had a case of mouth rot and he babied that dragon.  The dragon barely lived another year, but that year he had everything a water dragon could want or need.  When I asked about him, the vet said sadly that many times water dragons hit a certain age and they fail, usually from kidney failure.