Can't fix them...order new one and replace them. May have to use a heat gun to get the old ones off. Get new decals and contact a local commercial sign company to do the work for you. OR...you may have the local sign/graphics company just make new ones for you with a better grade of vinyl...more UV resistant. The ones from the factory are of the cheapest material you can get. i have graphics on a couple trucks that have been there for nearly 10 years...no fading or cracking. Make sure you agree with them you want the best material, as they too have the "good-better-best" grades of vinyl.
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie