Sounds like the axles need to be re-aligned. The camber is off if they are wearing on one edge, meaning the tire and wheel is slightly tilted to the edge that is worn.
Most RV repair shops cannot align the axles because they have to actually slightly bend them to do an alignment. You will need to contact a heavy duty truck and trailer shop that specializes in alignments.
If your RV is new and under warranty, the manufacturer may be able to guide you as to where.
I have seen where cheap tires can wear uneven, or cupped without being out of alignment if it's just one or two of the tires due to the belts letting go inside the tire.