PT Cruiser 2001 - Brakes (Autozone)

Ok here's the problem.

I've changed my own brakes forever and never had this problem.  I got 
new rotors and pads at Autozone.  Then about 6 months in I started 
hearing a grinding or groaning sound while braking.

I looked at the pads and they had tons of life.  I looked at the rotors 
and they were smooth.  Nothing seemed wrong.  I wen on driving for a 
year plus more just living with it as it seemed to stop well and it 
wasn't warn out.

I finally gave up and decided to get my rotors turned as they seemed 
weirdly worn.  The pad wore a groove the entire size of the pad into the 
rotor.  On other cars they seem to wear all the way out to the edge of 
the rotor I think.  This looked odd.  But, I turned them to totally flat 
  again and got new pads (for free because of lifetime warranty.)

I installed them all and viola, the noise was gone.  Cool.

Then about 2 months later the groaning is back.  There is no deep groove 
yet but they are wearing out the same.

A couple of questions:

Do others see that PT rotors wear out this way?  Wide groove.

Would the drum brakes in the back have anything to do with this?  There 
is no noise back there and I haven't changed them in all this time. 
They hardly wear out fast.

Might these just be bad rotors?  Soft like silly putty?

Don't want to reinvent the wheel (pun intended) or spend a ton on the car.

Thanks in advance.