Sudden FPS drop in multiple games
Solution 1:
I have this issue too with an i7 4790k and a GTX 970. However, not with the same games that you have included in your question.
But here are some solutions that have solved some users' problems:
Install EVGA Precision X and activate K-Boost on your GTX960.
Make sure you have every power setting (Windows, Nvidia) set to max and in every game.
Overclock your card and your CPU (Not recommended for laptops)
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Unpark your CPU:
Reinstall the OS (doesn't work most of the time)
Exchange your hardware (this has worked for some people)
Download Nvidia GeForce Experience and Optimize compatible games
Check for overheating on your components using MSI Afterburner
Make sure your computer is set to the GTX 960 (mistakes do happen and sometimes the wire is connected to the wrong GPU output, but unlikely non-the-less. Usually not a problem for laptop users though.)
If you have something like an Alienware, MSI, or the new Razer Blade Stealth, you can also buy an external GPU to drive the display instead.
This problem doesn't usually have just one answer. However, I hope one of these solutions have worked for you. And sometimes, this problem is just different for different users. None of them worked for me in Cities-Skylines while it has worked for others playing the same game with a similar system.
And if you looked at a lot of other forums, you will see people getting mixed results (however, some peoples' computers do get better) so don't expect this answer to be 100% better performance guaranteed.