opengl – CPU / GPU usage not high enough

I’ve been developing a c++ OpenGL game for the last couple of months.

A few weeks ago I was profiling the game and I noticed that the GPU usage was almost at 100% (with the framerate uncapped). I added a new feature and the GPU usage capped at arround 35% (also with the framerate unlocked).

At first I thought that this was about CPU bottleneck, but theCPU was also around 35% usage.
I was expecting the framerate to lower after that update (and it did, from about 2000 to 600) but I thought that the CPU / GPU usage would still be high.

Having the GPU usage this low makes me think that I should be getting more fps.

Is this behaviour normal or did I do something wrong?