Well, yes, time for new tires but probably not the way you are thinking. That should not happen for tires made in 2008. How do the other three look? I would contact the tire manufacturer and let them know. It is very hard to argue that curb contact caused that since it is practically the entire circumference. Based on the info you have given, you had to have had bad tires to start with. I think this an easy case for the tire manufacturer to rule in your favor. Good luck