Issues in Game Performance

[Mat_anu]

I am currently having a Major issue with my PC.
I custom built my PC(specs mentioned below) a While ago maybe around 4-6 months.

Everything was good. I built it mostly to play Games. i easily get 60+ FPS on my rig.
But from like a week am not getting 60+fps. The FPS count has decreased by like 50-60%.
I have no idea What's wrong with it. 

I installed MSI AfterBurner to monitor the temps and stuff.

CPU and GPU temps all remain in mid 60s. But what I noticed was that my CPU usage is reaching 100% in the same games I used to play in 60+ FPS. and GPU usages stays below 70%. No idea what can be the Problem.
 

Things I've Tried:

1. Formatting the System.
2. Removing and cleaing of GPU and Ram and Stuff.
3. No overclock.
4. Bios reset.
5. Disabling internal GPU form both Bios and Device Manager.
6. Updating Bios, Windows, Drivers and what not.

 

Nothing was changed before and after the format. Everything's the way it used to be.

 

Specs:
CPU :- i5 7400(3.00 GHz; Turbo- 3.5 GHz)
RAM:- Corsair Vengeance LPX 8GB 2400MHz
PSU:_ Corsair VS 550W
Mobo:- Gigabyte B250M-DS3H(MicroATX)

Hdd:- 1TB seagate & 500GB seagate (no ssd)

GPU:- MSI GeForce GTX "1050Ti" 4GB OC(single fan) 
OS- Windows 10 Pro 64Bit (not activated)

(1 Extra fan for intake.)

-Using a UPS

 

1 More thing I noticed was in the Task Manager whenever my system's ideal the CPU clock would be at 3.39 GHz or above(idk y it's soo high), but whenever I start a Game it decreases to 3.27 GHz.

 

Thanks to anyone who can help me fix this problem.
 

No app is using the CPU. 
No Background app running. 
Start-up apps are off. 
Power mode - High Performance.
 

Attaching Screenshots of CPU-Z, GPU-Z and HW+ Monitor.

 

And MSI AfterBurners Numbers During d game with CPU performance in Task Manager.

 

[Taswell]

does the task manager tell you what app is hitting the cpu like that?

[W-L]

-Moved to Troubeshooting- 

[Jurrunio]

1. Why a Corsair VS PSU. Why oh why oh why.

 

2. Decreased clock speed is just due to how turbo clock works. When the CPU has power draw headroom it goes past it's base clock and as high as possible but still within it's turbo clock. In your case, it just reaches its power draw limit, so it slows down a bit.

 

3. In Task Manager, click the "processes" tab, let it sort with CPU usage. This should show the CPU hogging software.

[Mat_anu]

1. I bought a Corsair VS 550 because of my budget problems. Everything was working just fine. No problems in turbo boost or anything. All of a sudden this all is happening.

 

3. At the time of gaming the game is the one Using it the most and nothing else is using the CPU.