Good Year CT failed?

I have a set of Good Year comfort tread on my 93 Lincoln TC that was installed back in 2007. It rides very smooth (not cheap) and handling is acceptable for this kind of a car. Last week I parked the car on the dark street where I could not see the curb, both front tires went over a pipe (probably 2.5") on the ground but only one of the tires developed a vertical crack on the sidewall so needless to say tire has deflated. When I came home I inspected all the tires and all of them have about the same amount of what appears to be a dry-rot. I will try going back to the retailer and have the tire replaced under road hazard warranty, but what should I do about the rest of the tires? It seems to be way too soon to have a dry-rot on the two year old tires and I am also not sure how safe would it be to continue driving on these tires. Any help you can give, please. Just wanted to consult with someone before I go back to the shop.
Thanks!

Comfortreds are a very slow selling tire. Check the date code on the sidewall. Maybe they were old before you bought them.

I can not positively verify the date on tires it says M6M3 18HR. I did go back to the tire shop and they wanted to give me peanuts for the prorated portion of my warranty - I put only 18k on them. So I ordered two Yoko tires from tirerack and it cost me $170 with mount and balance. That sure was expensive cup of coffee :shakehead

I also have Good Year Comfortread on my SUV, purchased in 2008. Have over 25,000 on them, no problems.
I suggest you contact Good Year themselves & explain it to them. I've been on their Web-site & they do have a "contact us" to click on.