124 brakes grinding, cant figure it out

[Grdenko]

Hello forum, long time no see.

Heres the deal, about 23k miles ago i got new pads AND rotors (front only), done by an indie shop. The pads i think are OEM type, the rotors are not though, theyre slotted, and rather expensive.

About 5k miles ago i started noticing a strange grinding from the front brakes. The grinding doesnt happen always, but about 1/2 the time under these conditions:
1. seems to be louder when theyre hot, but not necessarily
2. only at low speed, below 15mph, the slower the louder
3. the harder braking, the louder

this, of course caused me some concern so i put 'er up on a jack and took a look at the pads/rotors. Everything looked fine at first, plenty of pad left etc. but after closer inspection heres what i saw:
1. the outer pad was wearing significantly faster than the inner pad
2. the pads were wearing unevenly, more toward the outside edge

i dont know if either of those things is a big deal, but i thought i would note them.

here are my ideas about the grinding, it could be from the slotted rotors, but i never heard this grinding in the first 18k miles on them. or maybe the pads are a different type than i had before?

i dunno, but the noise drives me nuts so im gunna try changing the pads anyway, so id like to get some tips on changing them and what kind to use.

thanks for all of your help.