Late 2015 5K iMac frame rate

My wife and I are both running an iMac on game (using bootcamp for Windows 10 and Blade and Soul). Her early 2013 27 iMac (best upgraded graphic and i7 processor) runs the game (max) around 80-120 FPS mean while my late 2015 27 iMac (with the i7 processor and the M395X 4GB graphics) only ran at around 27-55 FPS. Both machine has 32 GB RAM. I wondered if there's anything I can set to test out to improve the frame rate for my late 2015 iMac. I tried to lower the resolution in the game to her iMac which is 2560x1440 but still gets the exact same frame rate.