So all was working and now has become slow - correct?
More information needed:
What make and model router are you using? (Or modem/router if combined.)
Any antennas or antenna extenders in use?
How far away is the router? What is between your "side by side" location and the router?
Access Points?
How many other network devices (wireless and wired) do you have?
What wireless frequencies and channels are you using?
Are you in an area where there are other wireless networks? Congestion and interference could be involved....
What speed tests are you running/using?
I do apoligize in advance for not being able to answer all this as some is foreign to me.
First you are correct. Although it is mainly my windows 10 machines, my mac seems fine.
My modem/router is very close (3-4 ft away from the Mac/PC's)
I use various speed tests, googles, att, ookla, xfinity, and fast.com. On my mac esp. the speed never changes unless of course I am using bandwith via streaming or downloading.
My apartment complex counting mine probably has 3 total, that I can see anyway.
I generally have 4 devices on wireless. 1 wired. Wireless: Phone, 2 Win 10 PC's and a Mac. Wired an Xbox.
As for make and model of my modem, i do not know as it was/is a issued one from a poor ISP company. Perhaps there lies the problem. Altho this is recent.
Thanks and sorry if I am not answering correctly.