I re-read your thread today. I don't know how I mis-read the first time and thought that you had an elderly dog, not a 14 MONTH old one. It's hideous to lose a dog that young and not have a clue what caused it. One thing my vet reminded me of was to be very, very vigilant about keeping ALL anti-freeze away from pets, even drips on a garage floor. It tastes sweet and is dangerous to all animals and children. If it's spilled wet/dry vac it up and scrub the floor.
Cockers are the sweetest dogs and Fiona Dos is a beauty. Those big brown eyes just say "you can't resist loving me". You'll never forget your first pup, but F.D. will find her own place in your hearts and lives.
Today is a gift, that's why they call it the present.