My Netgear nighthawk x4 wifi range extender is becoming weaker

4 months ago I have purchased a wifi range extender Netgear Nighthawk x4 dual band. I have plugged my pc ethernet cable directly into the extender. My internet speed at my router is always 100mbps and nighthawk used to slice the speed in half to 50mbps, which I understand because that's how extenders work. But now my pc is only getting 30-35mbps through the extender, even though my router is still outputing 100mbps. Does anyone know why nighthawk has suddenly dropped speeds so much? I have also changed some things in the registry editor of my pc but those shouldn't affect the extender right? I have tested speeds through nighthawk with my phone as well to confirm that my pc ethernet adapter was working fine.