Hi Mansfield, normally this yellowing (which can be quite common in certain locations, and although unsightly is not structural ) is simply removed after salt water use with a quick (very mild) rub with a household cleaner similar to what you would clean a bathroom basin with.Or similar. Even toothpaste. Or automotive paint cleaners (take care re these solvents etc though) Suitable (brand) products of course vary globally by location/availability.
Please check with your local dealer for best (local) advice, unquestionably the best initial contact with this (or other) warranty matters.
Cheers ~ Ian