Need more details to even take a stab at this.
- Have you installed the latest NVidia graphics drivers? (LINK) Did you do a clean driver install?
- Have you websearched about your problem, in combination with specifics about your hardware?
- How are you observing what your frame rate is?
- What OS and version?
- What PC do you have? It's not a laptop is it? If so, do you have the Intel GPU disabled, and do you have the power cable plugged in?
- Is your GPU the only GPU in your system?
- What monitor do you have? Same one across both GPUs?
- What screen resolution are you running? 4k? Try a lower resolution. Are you comparing the same res and quality settings across both cards?
- What motherboard? Same one across both GPUs?
- Take a look at your settings in the NVidia control panel. Note what you have; then see if changes improve things (e.g. disable G-Sync, multithreaded driver, triple buffering, etc.).