Black Spots on underside of Awning - How to Remove?

She scrubbed the spots with Clorox Clean-up. The spots aren't as dark, but did not go away. The other cleaning materials mentioned, we haven't tried as yet.

I googled "shotgun spores" -- thanks. I don't know if that might be what it is, but we do not park near mulch at the campgrounds we go to, nor at home.

I'm mystified at this point.

Thanks to all for your comments. Pls keep em comin'!