Any advice or input on my brand of tires?

I had the Vale Sport RT tires on my Camplite 21BHS. Took them from Florida to Arizona and Utah with no issues, and then from Florida to Townsend, TN. After the return from Townsend, I took a look at the tires and found a deep 4" cut in one of them with evidence of tread separation starting. Now it could have been caused by road debris, who knows. I had one tire replaced by Lionshead under warranty because of a 1 inch slit in the sidewall when new. I did get about 7,000 miles on the set before I replaced them. My camper is light (about 4500 pounds loaded) and is tandem axle, so I'm only running at about 65% of rated load. I replaced them with the Carlisle RH radials and there is a big improvement in towing.