I am using the AX1800 as a wireless router attached to an ATT router BGW320.  Wireless is turned off on the ATT router. I have 1000mbps up/down with ATT. If I connect my main computer to the AX1800 via ethernet, I notice the speed is significantly less than if I connect that computer to the ATT router via ethernet. It is ~400 +/- vs 800+/- on the ATT router. Is this normal or am I missing a config somewhere ?  Ideally I would prefer to have my main computer on the AX1800 if possible. 

Thanks

James (not a network guy)