| Most likely uneven pad deposition on the rotors....... Clean up the faces, sand them a bit or have them lightly resurfaced; then bed in the pads properly next time. Make sure they come up to temp before doing the hard stops.  Make sure you let them cool long enough before the next. Warpage is 99.9999% uneven pad dep on the rotors..... 
Cheers, Salah Aztec Red 300ZX Twin Turbo Platinum Mist Metallic 300ZX 2+2  
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