tried unplugging those two gtx 1070's and using their power supply cables for the riser and the rx 570, and suddenly it works. I have no idea if it is the cables or what the hell the problem is, and it is driving me insane.
try it vice versa, get the cables you use for the AMD and install it to GTX, if it doesn't work, you can throw the cables in trash bins. Lol, seriously its already faulty, if you're a techy guy you could check the wiring continuity with testers