Is there a fix for Frosted plexiglass

[polarlyse]

We have an '85 Excella. The window's that were double paned have had the inside covering removed. Some were done better than others but on the inside of the outter window there are what looks like mineral deposits. They do not wash off using conventional cleaners. This includes the fixed window adjacent to the door. Is there some way to clean / polish the inner surfaces of these windows. The outter surfaces look pretty good.

Thanks all,