The most obvious possible answer is that it is thermal throttling. Since the cpu and gpu share the same silicon die and same cooling, if the gpu is overclocked and the heat causes temp to increase, then cpu may throttle. To check if this is happening, monitor the temperatures.
well it goes at 61c 63 spike so I don't think it is it (I didn't rise the voltage ) and I have an aftermarket cooler (hyper t4) (I guess it is not that good but not that bad either)
So 63 is thermal throttling? (I can go to higher temperatures with cpu burner from fun marker and it will not down clock)