Hi,
If you've dropped or placed any cleaning cloths or wash brushes on the floor, then they'll have picked up fine grit - and will happily scratch acrylic plastic.
So only use clean cloths or wash brushes - a little bit of caravan cleaner in warm water - but rinse the windows with a copious quantity of clean water to remove any dust / grit stuck to the surface.
And if you do put fine scratches on the windows, then don't worry - just get a clean cloth and some Mer polish - apply and then buff the window - the light cutting action will remove those fine scratches.
Robert