Some hours ago (25th Dec) all of my rigs dropped ETH hashrate to -30/40%.
Regardless of miner software, the 1070 were hashing at 25mhs and now at 17mhs. Same issue with 1080ti.. from 45mhs to less than 20mhs.
I will try updating drivers, but this looks more related to epoch than miner/driver.
Probably windows update is turned on I guess, this always slow down mining hashrate, it's why windows sucks for mining, Linux and separate mining OS are way better, get hiveOS or ETHos for convenient mining