It looks like the the rudder has a clear coat paint covering. This peeling is probably a result of a nick or scratch letting the elements (water) to work itself under the coating which causes the coating to release. The spot just gets bigger and bigger. Another way this starts is simply the coating was thin to start with or wet sanding and polishing thinned the coating. Paint needs to be a certian thickness to be durable.

At any rate you should contact Marstrom and find out what they painted it with (or if they did) then you could go to any body shop and have them refinish it. Just make sure the body shop doesn't use power sanders to sand. It should all be carefully block sanded by hand to keep the shape.