Netgear CM1000 Slow Speeds

A few months ago, I picked up a CM1000 to replace the Comcast provided gateway I have been having issues with. Everything has been working up until recently when I noticed that I cannot get more than ~80 download and ~5 upload. I am on the Xfinity Blast package which gives 500/15. Before the problem started occuring, I was able to consistently get ~450 download over WiFi, and now I can't.

For troubleshooting, I have tested multiple computers and phones. I plugged a laptop into my router (Nighthawk X6) via ethernet and still had the problem, so I went through my modem and the speeds were still low. I am pretty sure it is Comcast's fault due to nothing being changed hardware or software wise in the last 2 months, but I do not have another modem to test with before I contact Comcast. I can provide modem information needed, but I'm not the most intelligent with networking, so that's why I'm posting.