xfi pods make wifi slow

I've had 2 xfi pods with the xb7 router for a few years now. Generally they worked great until a few days ago. Now my wifi goes in and out with speeds changing dramatically. My plan is 1.2G down and we can get close to that usually but when the pods act up it drops to single digits or worse. Computers connected to the router via Ethernet get full speed, so definitely seems like a wifi issue. 

If I reboot my router, the problem clears up for a while, maybe a couple of hours. Then it comes back. Unplugging the pods without rebooting the router seems to solve the problem. 

Like I said, this was working fine for a couple of years and now we are seeing this wifi slowdown several times a day. Looking forward to any advice.

-M