Netgear CM700 is 1/3 the speed of my Xfinity modem

Turned in old Arris modem to Xfinity 3 weeks back, bought a Netgear CM700 (Xfinity-approved). Speeds before were 343/22; now they are 91/22. Nothing else has changed, have reset and rebooted modem several times. CM700 is definitely rated for my plan.