Would appreciate the groups thoughts on tandem axle issue

Hard to say without looking. However its under warranty so call the dealer and get it back to them.

One tire on one side worn like that sound like the axle stub (usually where the axle stub is welded to the axle tubes) was bent like happens as the trailer is drug around a corner and impacts a curb as its side scrubs. Doing so can take the end of the axle out of toe and camber at that end only.

Or the tire was a run flat or at low pressures causing high heat and the tread cap came off.