Guys, I have a system with 5 GPUs, 3 R9 290 and 2 RX 480, all using usb risers with sata/molex adapter. He's been standing about 3 months 24/7. Today I smelled something burnt and found what is in the picture. Just the two that energized the RX 480. Do the RX 480 continue to extract more than pci_ex can support? Is there something wrong with my PSU?

My RIG:

Asrosk H81 Pro BTC
Intel Celeron G1820
8GB RAM
3 R9 290 + 2 RX 480(all stock)
USB risers
Cougar GX 800 + Corsair CX 750

https://postimg.org/image/an2rbk0wv/