I just cleaned the car up this morning after running at the strip last night and noticed that my front Rotors now have spots on them, looks like from being heated. The rotors have about 18K miles on them. They also are getting grooves cut into them from the pads (they are worn about 75%). I not really failure with this rotor so are these hot spots a sign to replace them or metal fatigue? I'm not getting any vibrations or other problems when I stop but I'm guessing they're about shot.