CPU, GPU, and RAM are all underperforming

[joefuz]

I've recently just put in a used GTX 1070 into my new pc (about 2 weeks ago), and it has been working fine, along with everything else in the system, but about 2 days I noticed a drop in frames, I thought nothing much of it and restarted my pc, but to no avail. From games where I used to get about 150 fps, I'm now getting 70 or lower, though still on max settings. I decided to run a few benchmarks yesterday, and noticed that, not just my GPU, but my CPU and RAM were all under-performing, like 20th percentile of average benchmarks, and my pc overall is in the 40th, I don't know what is happening and would like some help solving this.
Parts:
AMD Ryzen 5 2600X (with stock cooler, b/c I don't plan to overclock)
Asus PRIME X-470 PRO
MSI GTX 1070 Gaming X
500 gb Sandisk driver
G.SKILL Ripjaws V DDR4 3200 C16 2x8GB
EVGA 750W GQ series (80 plus gold)

 

[Obakasama]

I would start with MSI Afterburner and use its logging ability to monitor the various components: CPU (all cores/threads), GPU and RAM frequencies and usage; CPU and GPU temperature; fps and/or frametimes; and maybe page file. May want Ryzen Master for temps as well.

See if there's anything correlating to the drops in fps and/or extended frametimes.

Other things to maybe look at: verify game cache, any new updates to (I assume) Windows, virus/malware scan.