I am so sorry to hear of the loss of your dog Dex. I tragically lost a dog the same age and it was sudden and unexpected. I have empathy for your situation and we always wonder if we can do more. You loved your dog and that is the most important thing. Try not to be so hard on yourself, there may not have been anything more that could have been done to help his condition. I will say a prayer for your family and for Dex.