(I saw your reply just now while I was typing this... you already did this but I'm leaving this part in case it can help someone else.)
I agree, this can easily be the router. If you haven't already, power cycle the router. At the same time I'd do the same for the cable modem. If you're still having issues directly connect the modem to your best machine, power cycle it (so that it will grab the MAC address of the computer instead of the router's), then test directly connected. If we can establish that you have the same issue on more than one machine and you've eliminated your internal network variables (your router and cables between) then you may have a case for Rogers Cable.
So... again... more proof of TestMy.net showing results in line with the real world when others fail to. If it takes you about 2 minutes to download 1 GB then that's 8.53 MB/s or 68.26 Mbps... pretty far off from the 900+ Mbps the other speed tests tell you. Your TMN average right now is 84.9 Mbps. I assume when you download a file the speed during the transfer is fluctuating like it does when you run a TMN speed test.
It's lame that most ISPs no longer recognize the results here... especially since their techs used to send much more people here. In some cases TestMy.net was a main step in company training manuals. Before they had alternatives that made them look better.
Patrick07, I feel your love for the site. I sense that you already understand how it works around here. This is just general information for others reading.
Note: When you're running perfectly on 1000 Mbps... you'll still never see the the full speed here. Under the most ideal circumstance I'll see 990 Mbps but you'd never get those conditions in the real world, ever. The quoted speed that your ISP gives you is irrelevant to this test. You should use yourself (your best machine) as a baseline instead of what you think you should have. Like in your case, you used to consistently get over 400 Mbps then all of a sudden you see a huge difference. It didn't need to originally show you 900 Mbps to determine that there's a HUGE difference there. People get hung up sometimes because the results don't tell them the number they expect. They have 1000 Mbps and expect to see that, especially since every other tests tells them that's what they're getting. My goal is to give you a more realistic picture, including the variables you can expect to run into out in the real world. ... back to your own words. "Before, it (a 1GB download) would take less than 30secs." --- again, that puts you right at the 400 Mbps that TestMy.net was telling you. 400 Mbps or 50 MB/s... puts you at 20 seconds for 1 GB.
I'm telling you, demand that they take notice. Their speed test is obviously BS. If you feel like you've done everything in your power to make sure the issue is not on your end... force them to come out. They'll threaten to charge you but if it ends up being their issue... it's on them (make sure you get the tech to agree to no charge in writing, especially if they send a contractor). If you can't download from any source faster than TestMy.net results suggest, especially if it's confirmed on multiple computers AND you've eliminated additional variables like your router... AND you've gone through 3 different modems. They owe you a visit.