Thats why I always wait til afternoon about 6 or so sometimes after work at 11 at night to wash it. The lil water bubbles actually maginify the sun so it damages the paint.

I have had the best results with using a non-abrasive carnauba wax. Apply with soft material and remove with soft material.

To me it just looks like the water dried before you washed it..but washing it and then waxing it should do the trick. Try using a Pre Wax Cleaner like Mothers (sorry I'm biased ) which will get anything off the paint that washing cannot.

Then just dry your car immediately after washing it.

We have hard water where I live also. I wash mine either early in the morning or late in the afternoon and never in direct sunlight. I immediately shammy it (in the shade) so i don't get those dumb water spots.