Had a boat in the shop last year that looked like that… Centurion ski boat. The sides were flake and basically the gelcoat had so much porosity that he left it in the water off and on and it finally discolored like your pic… i’m not saying this is your problem buttttt. He did not want to fix it correctly so I just took it off the trailer sanded it several rounds and burned it in. It looked ok but the clear was discolored a bit and of course the porosity remained.