I cant get full speed out of my R6400v2

I have a R6400v2 Router I just brought along with a New Netgear modem with 32x8 for my new speed. When it was first installed I was getting my 400 down and 25 up. But now all I get is 190-200 down and 25 up I have tried factory resetting it and it would briefly get 400 but then return to 200 down a few min later or when I change the Default SSID. I dont have Qos enable everything is default. The tech came out and did a test after the modem and it getting the 400 but it something to do with the router. Any suggestion