Travel trailer uneven Tire Wear

I had that happen a couple years ago on my 5th, but it was one tire that the outside edge wore out of the 4, turned out to be a tire defect.  

I would be with Grit on this one, one spring that is failed would throw make the rv lean a bit but the tires and axels would be the same relation to the ground. 

what I would do is change the tires to opposite sides, if the tires if it is still in usable condition.  watch it over your next trips to about the same distance and see if the issue now pops up on the new tire.  if it doesn't then it may have been a bad tire, if it does then you need to look at your axel and spindle relation ship, and see if the axel has been bent to see if you can get a proper alignment, or new axel.  it could also be a loading issue but that would be my last though as that should just be hard on the whole tire not the one edge.  

another thing to note was the air pressure in the tires, was it properly inflated and so on.  and last but not least is the road condition.  if you drive on a lot of ashfault roads and the big rigs have cut tire trailes into them, is that tire riding for a long time on the edge of the tire swale due to your driving position on the road.  I have seen that take out more than one tire fairly quickly.