Sudden WiFi Issues, Lost For A Cause

Bit of backstory - we had some old modem with Bell, going to our Dlink 655 router. Everything ran fine. Bell told us our modem was -seriously- outdated and sent us some 2Wire garbage. It interferred with our router from what we gathered, so we just put it in bridge mode and other than the fact it CONSTANTLY would disconnect and we'd lose connection, and have to restart the modem/router to get wireless again, it was fine for the most part. We were fed up with constantly having to restart the router so we called Bell, who this time sent us a Homehub 1000. Still garbage. And that's what leads us to our problem today.

Before I state the problem - we've 7 - 8 devices connected to our router. 2 desktop PC's, 2 phones (Samsung Galaxy S4 & S5), 2 PS4's, a Wii, and 1 - 2 laptops although they tend to be off majority of the time. The Wii is also off majority of the time. We've ALWAYS had this set up, number and type of devices haven't changed. We currently have Bell as our service provider with a 6Mbps Down plan (Unsure on the up). We've one desktop PC wired. We're using a Bell Homehub 1000 garbage router in a "bridge-mode" according to them, with a Dlink-655 router, completely updated firmware. Anything I may have forgotten I'd be more than happy to provide you with. Our WIRED connection is rocking the expected 6Mbps down.

Bell had us fiddle with our modems a few times. It went from great to bad to worse. Again, the number of devices haven't changed. We used to be able to have two people on their PS4 while PC gaming and experience no lag. One person alone now experiences lag with PS4, although it can Netflix pretty reliably. The PS4's USED to get ~4 - 5 Mbps during their speed check. Now it's a struggle to even get 1 Mbps. My phone is even worse. It'll connect, I'll have NO other devices connected, and if I'm where I used to receive 3-4 Mbps, I now receive .07 - .30 Mbps. If I'm RIGHT beside the router? I'll get up to .78 Mbps. I can barely load a Web page, can't update Facebook, and downloading/updating any apps is a joke now.

I played with the settings, changed it from /g/n to all three individually, I used a wifi scanner to ensure there were no other access points in the area interfering, I played with the channels, first putting it on 1, then 11, then ultimately leaving it on 6. I've tried everything I can think of. We NEVER had this issue before, so I'm having a hard time understanding why the PS4's are having a hard time let alone my phone.

My desktop PC which is the furtherest item from our router with an older wireless card (Some old d-link model) is somehow getting 6 Mbps Down, .68 Up.

Why does this only seem to be affecting the PS4/phones, and why suddenly? What could possible causes/solutions be?

Thank in advance.