Noticed this also, was getting .0152 per day mining ETH with Claymore's Duel Ethereum Miner since last October and about two weeks ago it dropped to .00943 per day.

Hash rate of cards has not changed, just seems to be finding less shares.

Updated to version 10.6 and still same same results... I do not think its Claymore's miner.

What pool are you connecting to? ( us1.ethermine.org is what i have been on )