Black Spots on underside of Awning - How to Remove?

Our TT is only a little over a year old, and we never roll up the awning when wet. Still, we have a lot of black spots on the white underside of the awning. My wife has tried a few cleaning materials to remove the spots with only limited success. Our best guess is that some are squashed bugs and some are mold, which surprises me because as I said, we haven't put it away wet. One other factor, we live and camp in Arizona, so there are less bugs than in many states.

Could anyone please recommend cleaning materials to remove the black spots on the underside of the awning?