A little help would be appreciated.

I switched recently to mining Zcash from dual mining ETH & SIA. The problem is I can't seem to get maximum from my cards. I have a rig with 4x1070. From what I have been reading they should be able of producing 450 sols each. I get maximum around 420 from 2 cards and 390 from other two.

Cards are ok because all for of them were around 31 MH for ETH in dual mining (450 sia) no problem.

Any advice would be appreciated. OC settings: Is memory important or core or both? Which miner to use for best hashrate? Am I missing something obvious? At the moment I am using nanopool and EWBF's CUDA Zcash miner.