Stripes, decals and other hull additions are always a problem as time goes by. UV light, sea spay and nitrate based cleaning mediums such as Fairy liquid 8) will cause the surface to degrade. All plastics are susceptible to the marine environment and will degrade. Reds, Oranges, and colours at this end of the spectrum will be affected to a greater effect as opposed to blues, greens and colours at the other end of the spectrum.
You can polish out the oxidisation or white surface contamination, but, all polishing removes a layer of the surface, thinning the base material.
Having said that, Farecla G3 Rubbing Compound Regular Cutting Paste,
is a good medium to cut back the affected area.
Polish by hand, or better still using a mechanical polishing machine, then treat and polish with a good quality marine polish and hand finish with soft cloth.
Word of warning!
Cutting compounds can produce heat with mechanical polishing machines. You will need to lubricate the polisher foam & bonnet with water to prevent friction causing heat that can damage the decals or stripes.
By hand it will take much longer but there is less chance of damage.
As a guide or old Bavaria 32 (2003) took 3 hours to rejuvenate the top side stripes.
Hope this is of help.
If you need any help or need to borrow a polisher PM me.