are you sure you flashed back the original bios files for each cards ?
Did you saved the original bios file for each cards separately ( marked cards like 1 , 2 , 3 , 4 , 5 , 6 , 7 , and saved bios file for each cards like saved bios 1 , saved bios 2 ...., and reflashed the cards with the proper saved bios ? saved bios 1 to card 1 , saved bios 2 to card 2 , saved bios 3 to card 3 ...
Those cards might have a different original bios number version , and might not interchangeable with each other !!!
RX 470 /480 cards from the same manufacturer with the same model number can have a different bios file version number . I have many msi / sapphire rx 480/470 cards with same modell number , but different bios version number  ...

Did you modded your own bios files ? or downloaded from somewhere ? Are those cards have a dual bios or not ?
what crimson driver are u using ? what operation system ?
if you have a modded bios and using the latest amd driver , your system need a driver patch to recognize the cards or you going to the device driver error.

"The error is: IRQL_NOT_LESS_OR_EQUAL and the computer goes to the blue screen and restarts"
This error usually occurs after the installation of a buggy device driver, system service, or incorrect BIOS ( incorrect bios settings on the mobo , or incorrect bios on ur  vga card )