Dell XPS 15 9530 :: FPS Drops / GPU Throttling

So I recently bought a Dell XPS 15 9530 and well I wanted to see how it would do in gaming. It was doing well in most games until one day, I started getting fps drops that lasted a long time. The FPS would go from whatever it started with, an example being Watch Dogs with 50 fps on low settings, to 9 fps. Another example is CS:GO where I get 60 fps on highest settings, I cap it at 60, but after a few rounds it goes down to 15 fps. So I got NVIDIA Inspector to see what was wrong as many had said it was the GPU throttling and the clocks were 135 MHz for the GPU Clock and 405 MHz for the Memory Clock instead of the default 941 MHz for GPU and 2500 MHz for Memory. The temperature was around 75 degrees celsius at most so I don't think that is the problem. It is plugged into wall while playing and I have most programs closed down when playing.

Also, I have my power plan set to 'High Performance'. The FPS drop does not last forever but lasts about 10-15 minutes and can either be resolved by restarting my laptop or, if I am lucky, restarting the game. It is quite annoying and I have been testing everything for about 2 weeks. I have tried re-installing BIOS, clean installation of drivers, used different programs like ThrottleStop, tried lowering the settings and none of these have worked.