I cleaned the rotors this morning and picked up a clue - the passenger side wheel spins freely and quietly, but the driver's side spins not so freely and with a repetitive rubbing sound on each revolution. So something on that side is not right. The rotor looks straight but I guess it's hard to tell. I think I will try reseating the pads to see if that does anything. At least it's nice to know what side it's on. I'm also wondering if I can replace just one rotor since they are so new - less than 2k miles. Thanks for all the help.