What mining software are you using? I'm mining ZCash on Gibabyte GeForce 1070s and am getting slightly better results.

2x Gigabyte GTX 1070 ROG STRIX - Ubuntu 16.04 - EWBF ZEC miner 0.3.4b
Mem: +0
Clock: +0
Power: 100%
Avg Hashrate: ~438 sols/s per card

6x Gigabyte GTX 1070 ROG STRIX - Windows 10 -EWBF ZEC miner 0.3.4b
Mem: +634
Clock: +0
Power: 80%
Avg Hashrate: ~447 sols/s per card