Tire wear on tandem axle trailers.

This is my second season with this trailer (2006 Extream for a Malibu V-ride) and I noticed the other day that my rear tires have worn much faster than the fronts. There is almost double the tread on the front tires as compared to the rears! The axles seem to be straight, tire pressures have always been good. Only difference was that I switched to a drop down hitch late last season, the trailer wasn't perfectly level and was hard to couple with the truck sometimes, but now the trailer sits nice and level with my truck.

Any ideas out there before I talk to the dealer???

Thanks
Kevin