But if it's slowing down at the end of the month, my thought is it's not the router.
https://www.tp-link.com/us/products/details/cat-9_Archer-C50.html finds the usual not a gigabit router and I'm getting a lot of chatter about speed as connections go past 100 megabit. It seems the old designs (pre-gigabit) just have too many complaints when the speeds from the ISP go to 100+.
That doesn't explain the 10 feet issue. For that I'd check channels in use with my favorite Android WiFi Analyzer app. Read https://play.google.com/store/apps/details?id=com.farproc.wifi.analyzer&hl=en_US
Be sure your 2.5GHz channel is proper for your country as well as the devices. For some that can use channel 14 you run into that issue.
I can't seem to find an answer anywhere. I have upto 5 cell phones, 2 google home minis, 2 Roku expresses, TCL roku tv, 2 ps4s, 1 laptop, 1 pc, and a sengled light hub. A TP-Link Archer C50 router and a Arris SB6183 modem. I also have comcast with upto 250mb/s down. My tests usually put me around 150 down unfortunately. My issue is, my cell phone and laptop connect to the network perfectly anywhere in the house speeds are good, things like netflix and youtube work great, everything was working fine for the most part up until a few days ago, aside from one of my ps4's having to be hardwired to my router, just gave up on that issue a month ago. A couple days ago, my TCL started being really, really slow for netflix, hulu, and other apps like HBO, often timing out, but it was able to stream perfectly on youtube, 4k vids loaded instantly. I checked my other roku devices similar situation. My PS4s had touchy connections as well, even hardwired. I've power cycled, and reset my router and modem, with no resolve still only getting perfect connections on my cell phones and laptop, nothing else. This morning I woke up and now my rokus and google home minis won't connect at all. I've even taken all devices off the network and tried connecting just 1 roku device still the same issue. Called comcast as usual they aren't any help, they did inform me the last couple months I've gone over my data limit, from my calculations doesn't seem right, but good luck trying to convince comcast that. Just like typical comcast they said it shouldn't affect my speed I'll just be charged $10 for every 50gb over it's strange I always have connection issues toward the end of the month though especially on Hulu and Netflix other stuff will work great. I've tried stuff like changing my DNS on my router. I know things like roku's and PS4s have crappy wifi cards, thought maybe that was it, but it's strange they all got the same symptoms at the same time. Could it be my router, or modem cant handle the workload? Does anyone have any answers, I'm going insane. I did just order a Nighthawk AC1750 on Amazon should be here monday, I always did notice many of my devices especially roku devices didn't usually get a full wifi signal even with my router being 10 feet away from them.

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