@aromka 

I am wondering if the 2nd Deco is hitting the 1st Deco, then going to your "main" Deco.

You mentioned the 2nd Deco is in the floor above. Have you tried moving that Deco closer to the "main" so you would have something like:

                    <deco>

<main>                           <deco>

You can also swap the Deco units to be the "main", the app will just note that you need to designate a new "main" and choose the correct one based off of the MAC address.

Ah interesting, so ideally they should all be hitting main deco?

right now it’s setup like

                                                               <deco>

<main>-<modem>            <deco>

@aromka 

I would probaly move the Deco above closer to the modem as signal on the same floor should be good. It's when you starting going below floors where the signal can degrade.

With the Deco P7 the 2.4GHz, and 5Ghz use either band or the PLC (powerline) for the backhaul. Which ever avenue is faster to talk between the units. So the fastest possible mean would then have to go through another node to eventually reach the main unit. 

If you relocate the Deco above, you might have a stronger powerline connection and or Wi-Fi backhaul connection and should see better performance.

Side note, look at the LED light on the power adapters. If the light is green it is at a good location (above 50 Mbps). If the light is red, the PLC speed is low (below 50 Mbps) due to interference, cable quality, and distance. 

I will give a try.

Quick question about power adapter lights - I'm getting green on addon decos, but getting red on main deco - is that normal? or should I try another plug for it?

@aromka 

That can cause slowness, so ya, try a different outlet plug for the Deco, you want them all to be green. Avoid using surge protectors or any sort of adapter. The Decos should go directly into the wall outlet.