Question ref GPU percentage usage drop

Probably covered elsewhere, if so, apologies. Flying out of San Juan this morning in the A320 NX. Beautiful sunrise, FPS steady mid to high twenties internal view. Then, rapidly, FPS dropped to single figures, not a “stutter”, this lasted several minutes. I activated my Task Manager and noted that the CPU usage was in the high 70 percent range but the GPU was only in the teens percent. Then, whilst I was watching, the GPU percent rose above thirty percent and the CPU fell to about 50 percent and the frame rates recovered to high twenties internal and over forty FPS external. Is this is what is called “bleed” ? And what causes it, is there a way to limit this effect?

be sure to check this that you see the correct GPU load