Charter is absolutely terrible (screw the "Spectrum" rebrand). Unfortunately in my neck of the woods, they are the only ISP without a bandwidth cap AND they offer the fastest speeds, by far.
I am constantly having problems with their terrible internet service. I've mostly lived in the same area for a long time, and it didn't used to be this bad, but the service was never good and it's too expensive (having used their cable internet since around year 2000 here). They've even had the same upload speeds since roughly the year 2000 and they are stuck on 5mbps UP which is fricken terrible in 2017. Anyway, I've had numerous symptoms. One included my internet slowing to a crawl even though I'm supposed to be getting 60mbps, having random days where it's stuck at 3mbps all day. We don't get their TV service (because we don't want our bill to be $170/mo) and stream everything using Chromecasts, Netflix, Hulu and Amazon Prime. So when our internet is this f-ing slow we lose TV too essentially. To solve the issue we had to call and I had to deal with a robot A.I. for a half hour before finally being allowed to talk to a real person, who immediately noticed the difference and fixed it by remotely resetting the modem. Unfortunately, that didn't totally stop the problem, and within a month's time we had very slow internet again for a period of days. We finally called and a tech came out, he was only here 20 mins and didn't even come to the door, did something to our line on the side of the house and it's been mostly good ever since. I read on NextDoor here that they talked to someone and they told them that Spectrum works differently now and there is legacy equipment attached to some houses from Charter and it can cause these slowdowns. I'm betting that's what the tech who came here did, removed some junk and it fixed the problem.
They are also constantly having issues with our network and our city. During peak hours (6pm-8pm), oftentimes our internet slows to a crawl. Simply put, the infrastructure isn't really there to support so many houses with the service. We are very behind countries like Japan and Norway in this regard.
They sometimes also like to take the service totally down so my modem won't connect late at night, (3AM or so), when most people are asleep, but when I'm usually awake watching stuff on my couch.
Your problem, however, sounds more like the effects of this NetBalancer program. Make whoever is using it uninstall it. Check to make sure people aren't downloading large files simultaneously or streaming HD video on multiple computers (the Charter line can handle this at full speed but your router and Wifi probably can't if multiple computers/phones are doing this at the same time). QoS is a good recommended solution if your router supports it. If stopping this activity doesn't solve the problem, you may need to run speed tests (Speedtest.net) to make sure you are getting the full speed you paid for from Charter. If not, then you may be experiencing similar problems to what I did and may need to call Charter to resolve the issue.
Hope this helps.