Goodyear Marathon Sidewall Depressions

Like many of you I have had tire problems, including an interstate blowout last month in South Dakota. Before my most recent outing I bought new Marathons. Not because I was thrilled with them, but because the choices for trailer tires are so limited. We returned Tuesday from a 1700 mile trip and I cleaned the TM today. Noted that the street side tire has two significant sidewall depressions extending from near the outer edge of the sidewall (just below where the tread stops) to the rim of the wheel. These depressions are about the width and depth of a man's little finger and are almost 180 degrees across from each other. The curb side tire has one less pronounced depression.

Anyone else noted anything like this? Does anyone know if this should be a cause of concern?

Thanks in advance.

Bill in Tennessee