I've never used the Meguires protectant, but I'm thinking it might be reacting in some way to the existing clear on the lenses.
I've always just cut plastic headlights down with 800 or 1000 grit then gave them a shot of 2k clear.
But if you are having issues with fisheye cut just the fisheyes down and polish and re-coat. If the meguires is anything like paint a re-coat like this should reduce the fisheye.
Does the meguiers can say anything about humidity or temperature?
Just thinking out loud here.
