The dark brown gelcoat front cap on my 2015 Winnebago Vista faded as well, and this was a quick fix that worked for me ...
I am scared of trying to use a buffer to try to buff down thru the gelcoat to unoxidized finish which seems to be the longer term answer from what I have read, and making things worse if I remove too much of the gelcoat material.
I lightly sprayed WD40 on a microfiber cloth and rubbed the gelcoat to a uniform dark color, then wiped with a clean microfiber cloth to remove all surface residue of the lubricant. This either removes the oxidized surface layer or at least treats the discoloration of it.
Then, I applied NuFinish One Step Polish, a wax free coating product, to a microfiber cloth and rubbed it into the gelcoat and buffed off excess with another clean microfiber cloth. This seems to seal the now dark again surface layer and keep it from returning to the discolored oxidized state.
I expect it will be a temporary fix that I will have to refresh at least once or twice a year. But it makes it look good for a season.
Randy - Manhattan, Kansas
2015 Vista 27N
2020 Ford Escape Hybrid