It sounds like you have the same problem.
I ended up having two sets of rotors. I turn them once before I throw them away. You will be told that the rotors cannot be turned. It is up to you if you have money to throw away. My preference is to at least turn them once before I dump them.
Then again, I don't have cheapo ones, I have the cross drilled Zimmermans.

Make sure the wheels are ALWAYS torqued, specially when you take your car to a shop. This is #1 reason for warped rotors.

By the way, it is very difficult to tell the difference between front an/or rear warped rotors.
Check all of them.