I recently had Youfibre gigabyte broadband installed at my home.  The router is in my office.  I have set Mesh to access point mode.

My home has a cat6 network installed and I have x3 M5 devices.

The cat 6 cables all feed back to an under stairs cupboard.

I have set up the M5s in the following way.

Router connects via cat6 cable to Main Device.

Main device then connects to understairs device directly via cat 6.

Understairs device connects to lounge device via cat6 cable. (This often reverts to MiFi)

I have ~ 945 mbps coming from my router to main device, however, the WiFi speed from all 3 M5s is below 450 mbps.

Is normal for there to be such a big drop?  Have I got the set up wrong?

Any help appreciated.