Plexus will bring back clarity since it makes it shiney by adding a film, making it shiney makes it clearer. I bet Pledge works similar.
Scrathes are another issue. I don't bother with them, tried in the past, water under bridge too late now.
And when storing off season, make sure canvas and windows are bone dry before rolling up. I lay them out in the sun all day after morning cleaning. And the windows shouldn't touch eachother, they can stick together.
I use WD40 on zipper sliders, works fine. Mitigates corrosion of the white metal.