Sail it first and see if the discoloration affects sailing :)
But if you're bored ashore, go least intrusive first.?
1) Dawn dishwashing liquid soapy water and let the sun bleach it a bit.?
2) TILEX but do not let it sit too long or dry.
3) 3M Fiberglass Restorer and Wax
4) Wet sand with 1200 then 2000 grit followed by a good past wax like Meguiars
*) Iron Out Rust Stain Remover gets rid of mineral stains. READ THE PRECAUTIONS and wer Personal Protective Equipment
Of course we need photos!
Cheers
Kent and Skipper
Signal Charlie