spider cracks are fine, just keep an eye on them after each session. My buddy has about 10 track events on his rotors with spider cracks and they arent breaking apart. Spider cracks arent too uncommon. Now once you start seeing radial cracking, or you can catch a fingernail on the cracks when running it across the rotor, it's time to retire them!

off topic, but did you get to upload any of the Daytona PDX pictures?