Very sorry to hear that Dave. Kind of strange on the big pond kill vs not the small or creek. Does the creek feed the small pond? Maybe it created a higher DO saturation in the moving creek water, and that fed the small pond?
I've heard the phrase 'misery loves company'. What a load of horse pucky. I wouldn't wish anyone joined the 'kill club'. It takes a while to get perspective on what you control (which isn't near as much as we like to think) when it comes to our ponds. Don't spend too much time worrying about it, and start planning for the next generation of big fish you'll grow.
Hang in there pard.