only 1 of my 4 tires is worn off on the inside

I had the same problem once with only one tire wearing.

This is what I found causing the excessive wear.

Several years ago while going from Flagstaff to Albuquerque I had an axle collapse. It was replaced by Lippert but it was due to some very bad chuck holes that I could not miss due to the size of the chuck holes a very heavy truck traffic.