Mercedes rotors are not intended to be turner or ground.
Check fastlane or partsshop here for new ones if you suspect the discs.
I replaced both front discs and pads on my 300ce, Pretty cheap For peace of mind if you ask me.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.