Tire Sidewall problems of the 2000 Acura TL

I have 4 gt radial champiro touring as 205/60r-16. They have all formed large cracks along the lower sidewall. The tires were installed 1. 5 years ago. I feel that these tires are unsafe and at risk for a blowout. I cannot drive the vehicle due to these tires. The dot # is y9j5crvx4115 on all 4 tires. These are structural cracks not cosmetic.

The contact owns a 2000 Acura Tl. The vehicle has sunny sun 3800 tires, size 225/40/zr18 (na). While driving approximately 30 mph on normal road conditions, the vehicle began pulling in one direction. The driver pulled over to the side of the road and inspected the vehicle. He observed that the front driver's side tire exploded. In addition, the sidewall of the tire exhibited severe cracking. Roadside assistance was called to the scene and they replaced the tire with a spare. The vehicle resumed normal operation and was taken to an authorized tire shop. The technician stated that they were not responsible for the replacement of the defective tire and it was not in stock. The vehicle was taken to a different authorized tire shop for a second opinion and the technician stated that the defective compound contributed to the sidewall failure. The four tires were replaced at the contact's expense. The VIN was unknown. The failure and current mileages were 171,000.