Strange, really. I have 580 8g (hynix) cards i tested the miner on , and i get the same hashrate on V7 as on previous versions.
There are always HR fluctuations, and always will be, that's why i ask for the 30 min average, and not the value you get when pressing 'h'.

Same rig, same driver, same everything except miner version?

I will check to see if any of the changes i made could cause this HR drop.