Mobo: Asus Crosshair VI Hero
CPU: R5 1600
GPUs: 2x R9 290
Storage: 1x nvme m.2 SSD, 1x SATA3 SSD, 1x SATA3 HDD.

Radeon software tells me the GPUs are running in x8 x4. Everywhere I read, they should be running in x8 x8, still leaving x4 for the m.2 and 4 spare PCI-E lanes unused. How can I troubleshoot/force the 2nd PCI-E to go x8?

In the bios settings, I could only find controls for Gen 1 Gen 2 Gen 3 etc, not how many electronic lanes assigned.

[EDIT]: Somehow the problem solved itself. I did some GPU re-seats and some clean driver re-installs (with Express instead of Custom) over the past day, while trying to solve some other issues, but went back to check and now this is solved too. Anyone else find this thread in the future should start with these steps and mayb reply with exactly which one helped.