Flying problem when rtx on

When flying in elytra or just creative mode, the FPS drop under 10 (I'm at above 90 everytime).
I don't know if it's my pc, but this is the only game where it happened (i bought my pc 2 month ago).
I think it's because of the GPU's % which is dropping to 20% instead of 95%+
But still, i don't know if it come from my pc which is badly configured or the game itself

Gpu : RTX 2080 Super
CPU ryzen 7 3700x
Ram : 32 Go, 3200Mhz