so, i got both rear rotors machined and brake pads replaced (under warranty) because the brake pads were overheated and glazed it.
after driving around for less than a week, i noticed that the rear passenger rotors were perfectly fine but the rear driver's rotor has really deeply etched rings. here are some pictures... btw i initially brought my car in to the dealership because the rear driver brakes were screeching.
one of my friends guessed that it's caused by the ebrake being partially engaged which is causing the deep etched rings.

okside



damaged side

 

i have that on my front right brake and it squeaks!