As was said, if the trailer wheels are in the correct alignment and the axle is not in overload, all 4 should wear even. Other than ST tires in the tandem setup can have side turning wear on the outside corner from road scrub in the turn. More like a radius wear rub on the outer tread corner. LT's in this same setup do not seem to do that as pronounced like ST's from what I have seen.
That said... you have an RV... Is this the first set of tires on the camper? Is this the first time you noticed wear?
It may have not been build right to start with and the other tires may have wear patterns too, just not as pronounced.
Some truck shops or trailer shops have trailer alignment machines and they can check everything. Before a fix can be done, need to know what is wrong.
I agree, get all 4 wheels weighed separately is best. Odds are high one wheel is heavier than the other.
If you want get into doing some checks yourself, let us know. There are simple ways to check for an axle which has loss of camber and some times a bent stub end which the axle tube is OK but the stub end is bent and the wheel is out.
Inside wear on a trailer often points to camber and/or the toe angle that is way out of spec. for that wheel. Causes can be several in how those conditions came about.
I myself would check it out before putting new tires on.
