So sorry for your loss! It is so hard to lose a pet so young!

My first tonk died when she was 6 months old- FIP was officially blamed for it, but I really suspect that she may have had something genetically wrong with her (as my mom put it "a failure to thrive baby". Luckily, my 3 year old Sina (the breeder gave her to me after my Charlie died) is a hearty little girl. I did see it mentioned on the Tonkinese Breeders Association page that they sometimes have trouble with anesthetic. Good thing I didn't know that before Sina got spayed- I was a total nervous wreck as it was!