it dosnt sound like a power supply issue. the new amd drivers in windows dont allow for bios mods and im thinking thats where your issues is.
So why it would it work forever and then just all of a sudden not?
Also, I can have one card running just fine. That doesn't make sense to me? But, that doesn't say much, I am a noob.
Then it may just be a single card try them one at a time till it breaks. I said a simmilar issue turned out to be a riser issue. Your riser may not be getting enough power. Or could be using to many resources for your rig there’s a script somewhere online that disables everything for mining using less resources could be a bios issue on one of your cards your only option is to troubleshoot one thing at a time till u find it