My incoming signal from Spectrum enters through their modem and is wired to a separate modem then to the router.
So you have 2 modems?
Try this - eliminate the router and just go from the modem to your computer and run a few speed tests, You should be getting near 70
Now if you try it again using the router you should be getting pretty close to the same speed. If not then its your router thats the problem.
I have close to 30-40 different wifi connected devices alone and pay for 100 speed and just ran a test and I get 125.
I also have security camera but they are POE and not wifi.
See if your router has a firmware upgrade. You can always unplug the router from the power, wait and let it reboot. If this has just been happening in the last few days it could just need a reboot.