If by "not even after a year" you mean the rotors were brand new and after less than a year this issue arised, check with where you bought them about warranty/defective. There have been cases of bad lots of rotors from different manufacturers.
Other than that, never turn rotors, thats the consensus opinion.
Also check mis installation that could of caused the warping.
Current
2008 M5 6 Spd
2000 Z3 2.8 5 Spd MSport
2012 X5 35d Sport
1995 540i 6 Spd
1992 535i 5 Spd
Former
1995 530iA
1986 635CSI 5 Spd
2011 X3 2.8 MSport