Saw this on the front rotor of my 99 LS 400 today. Rotors are Centric 12144107 from RockAuto and installed about 9 months ago. Most recently it's sat outside for a few weeks until I could replace the fuel pump, so I know thats where some of the pitting is from.

This line looks very strait though, it's not from the brake pad as that would have some curve on the ends from it sitting. Just wanted to see if this looks odd to anybody else...



thinking of going ahead and replacing them just to be safe.

 

Figured it out...it was the groove in the middle of the brake pad. I took the tire off and could see the whole outline of the brake pad so mystery solved lol.