what's the clockrate of those 3 ants? also did you distribute the load or just plugged into vga ports on that psu?
I have plenty of ants running 3x to a Corsair HX1050 very reliably with cool cables, pulls ~1000w at the wall.
Also running 3x to the EVGA 1300w g2, ~975w at the wall to 985w at the wall.
2x to RM850 - 760w at the wall
2x AX860i - 740w at the wall
2x AX 760i - 760w at the wall
1x CX750 - 455w at the wall to 435w at the wall
Hope this helps people.