Chose to render with GPU(CUDA) but only 30% utilize rate but 90% CPU usage

I made a 4k 60fps video around 14 minutes, but it took entire 2 hours for an RTX 2080 to render, to my knowledge, this is not correct, I checked task manager and both 2080s are at around 30%, but CPU is to 100%, is there a way to make media encoder to fully utilize my RTX 2080s?