Suddenly Very Slow Speeds on my Nighthawk X4S AC2600 R7800 Router

hi

Same as another thread i have seen. Wired connections sudddenly only giving me 50-70 Mbps on speedtest. sued to get 250 easily

Runnign speedtest from build in speedtes in router still give me 250 Mbps. But devices behind it get much lower speeds. Which did not use to be the case. Anyone have any idea? disabled QoS but that did  not make any difference and am on latest firmware 1.02.82