Object is out of the sceene but fps is low

Hi all,

I have a question regarding rendering performance. In my game are appearing 'fractals'- big (>7000) objects and every part is rotating on random angle and with random speed. I'm measuring FPS and when I do not have fractal on my screen average is around 70, when object is apearing FPS average~30. And it is fine, but my question is: Fractal apears on screen but when I'm moving with my player and camera view into the place where I cannot see this fractal FPS are increasing only on 2,3 fps. Is this object kept in some place in memory? Why Culling is not avoiding this type of issues? I can just add that I'm using automatic options of camera and render.

I would be very gratefull if you have any materials regarding rendering the screen and object out of the screen. Thank you very much and best regards, Kamila