Re: Overtorqued the lug nuts?
Overtorqued lug nuts is a definite suspect in many rotor warpage cases.
Better tire and service shops have a policy of using a torque wrench to do the final tightening and in the proper sequence - star or every other bolt on a five lug pattern. The spec is in your owner's manual.
If you are considering contracting with a shop that does not use a torque wrench to do the final wheel bolt tightening, you should take your business elsewhere.