rlavalle - Russ, an easy indication is by looking @ the thermal indicator paint on the edge of the rotor. If they've turned color and the metal on the rotor had turned blue, it would mean you past the "limit" so to speak on the specified heat range.
By the looks of the picture though, it looks like your PF pads may have been leaving residue on the brake surface, which would attribute to higher surface temps. (what series of Performance Friction are you using? Have you checked your pad to see if there's "chunking" of the material @ the surface? This would indicate that this pad compound is not "hi-temp" enough for the type of track)
Before using them the next time, take some sand paper to the surface of the rotors to "buff-out" the surface, this will help to clean off the area to make sure maximum surface area for heat dissapation is available.