hey guys, I just installed new slotted rotors onto my camry 03 v6 with ebc green stuff brake pads. The front pads that I bought fit in just perfectly, the rear ones though, not so good. They didnt fit at all. I then resorted to using the old pads that came with the camry (which had a pretty good life left in them) in combination with my new rotors. Here are some pictures of it. My question is, because the new pads had break in padding, am I harming the new rotors by using the old pads? The wear seems quite uneven.

(here are my front slotted rotors)

(here are my rear ones)

(that is my rear rotor after test driving it around a bit, notice the thick line of wear that is toward the center of the rotor :\)
any advice would be appreciated, thx!
p.s: these rotors are brandless and ebay bought.