@Mikee46 

Hi,

If you've got a Mesh consisting of an Archer C80 and two RE300 and you want to test the Wi-Fi performance of the Archer C80, then I recommend to pull the two RE300 out of their sockets (i.e. power them off), take your iPhone or Samsung to the room where the C80 is located and then perform the speed tests. Make sure you are connected to the 5 GHz band.

130 Mbps download speed sounds more like your phones were connected to a RE300 at the time you performed the tests.
 

  @woozle will try that now!

  @Mikee46 

Then it gets more complicated.

If you suspect a settings issue, then you could try the following.

1) "Backup" the Archer C80's settings to a file on the disk via the menu "Advanced" -> "System" -> "Backup & Restore".
2) Perform a "Factory Restore" from the same menu.
3) After the Archer C80 has rebooted connect to the 5 GHz Wi-Fi using the default SSID and password printed on the label. (in case you are using a PPPoE connection then configure it now, but don't change any other settings)
4) Perform a speedtest.
5) If the Wi-Fi speed is still low, then "Restore" the settings from the file you saved in step 1)

Now the router should work as before again.