Ok. So you saw where the thermal pads were and simply replaced them. Nothing wrong with that. Not sure why the original ones "melted" though. That's a little concerning. May need to elaborate more on this.
When you replaced the thermal paste, did you clean the old stuff off (with rubbing alcohol on a paper towel) both the GPU chip and the heatsink before you applied new TIM? How much TIM did you apply? (Half a grain of rice is the correct answer to this question)