More likely the exhaust in spite of other comments. I have internal sensors on my trailer so they are insensitive to sun and wind effects. And in spite of the distance the ones behind the exhaust are always hotter with the front trailer tire hotter than the rear. But it also depends on which side your exhaust is at, mine is curb side, or with dual exhaust depends on wind direction. When I searched this issue I found one owner that had melted plastic trim at the lower corner of the fiver when towing during a regen cycle. I don't think a 10 degree diff really matters, worst case maybe rotate tires side to side.