Well... i think you need to work some hours to optimize your rigs. It´s not so difficult and you´ll get much more hashrate and less power comsumption (this means longer life for your gpu´s too).

This is a present for you, a complete guide step by step to tune up your rigs:  https://mining.help
It´s writen to improve your ether rigs, but there´s a tab with the xmr/criptonight settings.

Regards.