you could try with a bit of sand paper on some wood "a flat surface" and then give them another try, tbh it just sounds like your pads have contoured to your old rotors so flatting your pads down a little should do the trick

*edit* or if it doesn't bother you another set of pads would cure it straight off, but depends if there is still alot of meat on the old set and don't wanna just bin them