Dell XPS 8700 performance got worst! Please help!!!

So I bought the xps 8700 two weeks ago and got it set up last week. The main goal was to use this computer for minecraft youtube videos. The first time I tested it out, I got around 100 fps when recording with dxtory, but 1 week later and I'm only getting around 50 fps when recording. So as you can already tell the performance has decreased a lot within that 1 week. I checked to see if there were any viruses and there were none. I also defrag the hardrive and ran the disk cleaner, but still not helping. can anyone please help me? Thanks! And also sorry for posting this in the laptop section... Didn't realize till after I wrote all this.