Wow, this is surprising given these games all can run on old hardware.
Tell me, with the settings and resolution as low as they can go, does your FPS stay the same or dip?
If it keeps dipping, open task manager and monitor the CPU. While FX isn't a steaming heap of garbage like users make it out to be, it's main fault is single thread performance. If you see one or two being pushed to the limit, then it's the CPUs problem.
Also, do monitor your temperatures. If the CPU or GPU are running too hot, safety features kick in that make them tone down performance and stop using as much power (which reduces heat generation, giving it the opportunity to cool down) If that CPU is overclocked on a low end cooler, I recommend turning it back to stock settings and seeing what that does for you. It might be getting even hotter than before because it is summer.
I can confirm with Borderlands 2 and PAYDAY 2 with an FX-6300 and an RX 480 before I gave the CPU to my cousin, I had some minor dips usually during a change of scenery, nothing more (1080p, maxed out settings) So it's either the 1050Ti being a bit too weak or something's throttling would be my guesses.