I have several 1070s.

When setting up a rig, I tried a single 1070 on a spare PC. I was getting 1400kh/s.

So I built a rig with multiple 1070s and each one now is getting around 800-1100kh/s. I am also getting a message: "share doesn't validate on CPU"

I am using cpuminer-opencl with command:
minerd.exe -a wildkeccak_ocl -o stratum+tcp://bbr.mbkpool.info:7777 -u  -p x -k http:///scratchpad.bin -l scratchpad.bin

What is going on? I have the most recent nividia drivers.

I am running Windows 10

TIA