Had the same issue with the front axle on an 04 Boatmate chewing up tires. As others have said, previous owner probably ran it with the hitch too low or did something which put undue stress on the front axle causing the ends to bend upward.
At the time, I replaced the spindle assembly on the side that was worse hoping it had been tweaked at some point, etc. but it accomplished nothing. Save yourself the headache and replace the whole axle. With your 18's any minor misalignment will kill your tires in no time.
Might as well service the bearings and flush the brake fluid while you're in there. Mine looked like Jagermeister
completely black. Brake fluid collects moisture and eventually rusts components like calipers, etc making them stick.
Personally, I would keep running it through the end of the season and rotate the tires for even wear then get it handled over the winter.