My goldfish pond has had happy fish in it for 4 years now and suddenly I've
had 2 of them die within a week. No signs of disease or trauma...I live in
south TX where the temp has averaged 100 lately, I'm wondering if the water
is too hot for the poor guys. I know they do best in cooler waters.

The warmer water gets, the harder it is for gasses (including oxygen) to
stay dissolved in it. Heat can be a problem... and so can suffocation.

One prescription is to make certain the water is circulating at all
times; it is particularly helpful to move the bottom water.

Heed the other's advice; get a thermometer and a shade canopy.

You can make a temporary and cheap shade canopy with PVC construction
pipe.

If you're looking for something more aesthetic, you might build some
kind of trellis that sits between the pond and the southwest.

C//