Rear Tires Worn inside

I'm seeing a lot of wear on the inside of my rear tires, but we have solid rear axles... Has anyone else had this issue or maybe know whats going on?

Some info about my truck: 2017 TRD OR DCSB, with BFG KO2s on Method NV wheels.

I had the wheels mounted/balanced by America's tire back around May of last year.

Interested to see if anyone else has had this problem..

Edit: (picture shows it mounted on the front, just got a tire rotation)

 

Is it just one or both doing it ? You have the correct psi in them ?

 

Both tires are worn equally which tells me probably not pressure. I try to check tires every 1-2k miles, they may have been running a few psi low but not much more than that.