Windshield Haze

I've noticed that the windscreen and canopy on my RV-6 has developed a haze
on its exterior.

The history of the canopy is that the canopy was manufactured about 7 years
ago, with the airplane first flying about 5 years ago. The airplane has
always been hangared (other than the occasional overnight stay somewhere),
and has been treated properly during its life. My cleaner of choice is
Plexus, which Aircraft Spruce and several other outlets sell for aircraft
canopies.

The only things I can imagine that could have caused the haze on the canopy
is either the plexus, exposure to corvis oil (the smoky stuff) at airshows,
or some sort of airborne contaminant in my hangar (e.g. a neighbor spray
painting).

For what it is worth, the canopy doesn't have any scratches, so I probably
don't need an aggressive abraisive cleaner.

The bottom line is that I'm interested in removing this haze layer. Any
recommendations?

Thanks,

KB