Oh, I forgot to mention the problem why I decided to ask for help. My hashrate is about 180mh on each rig. But my effective hash on pool 160-170mh. That's my problem with that. And it's not overclocking, I see that the hour of cards in rig always gets more shares per hour than some other cards. I have already perfectly adjusted the frequency of all cards, but the loss of 7-10% hasrate does not go away.

How many shares per hour do you give an average of one rig per 180Mh? I have on good rig 160 but mostly 140.