Why would a polycarbonate skylight haze to the point it looks like frosted glass?
Background: North Florida (Gainesville). About ten years, my mom replaced the glazing on the large (about 2.5x5') skylight in her kitchen with polycarbonate, partly on my recommendation. This was done by getting the piece of polycarbonate cut and fitted into the existing skylight frame, which dates from when the house was built in 1956, not by installing a new skylight. My mom died last year, and my sister is now living in the house.
Today we noticed that the skylight is severely hazed, to the point that it looks like frosted glass. Some of this could have happened gradually, but to the best of our memory it's mostly recent. Here's a photo looking up through the skylight
The top of the skylight feels rough, and looks rough under slight magnification:
We tried a couple of forms of gentle cleaning, and nothing helped. It even continues to look just as hazed with water on it.
While it's true that there are advantages to diffuse light, in this case the views are good enough that we'd rather it be clear!
Any ideas why this has happened? Or what we could do to prevent it, if we replace the polycarbonate?
Edward