I actually had this happen on my stock Michelin's. I went to try and get them warrantied by a Michelin dealer and the dealer called it Ozone Drying and Cracking, something they did not cover because it was not a safety issue, so your fine in that respect. They do look like crap with the cracks in them but I guess you can't really do anything. Are you also getting browning with your tires? I have pretty bad browning, which again doesnt really compromise the tire but it sure looks like crap hah.
Brandon