Sudden slow downloads over WiFi?

Hey guys, for the past few days my download speeds on pro have been really bad. I first noticed somehting was up because The Apple TV app suddently wouldnt connect and
says to test my internet connection. When downloading a game it says ‘calculating’ for ages.

I don’t understand why, nothing changed, my router is receiving the full 1.6gbps download speed, every other device in the house (phones, tv, desktop pc which is WiFi) all work fine at the correct speeds.

I’ve changed my DNS manually (tried 8.8.8.8, 8.8.4.4, 1.1.1.1 and 1.0.0.1), made sure to select each ghz band individually to test and restarted my router but no dice.