Correct me if i'm wrong,seems like your PSU can't handle that 2 GTX 970 . As i seen on Guru3d.com , they said that "
"GeForce GTX 970 or 980 in 2-way SLI - On your average system the cards require you to have an 800 Watt power supply unit as minimum. " You should use Cooler Master PSU Calculator to check if it enough power for your system.