I am seeing the same thing, except with Lyra2RE2.  I have been hashing it for 5 hours and the last two have seen a massive drop off in hash rate.

Edit:  Seems to have just started working again.  Perhaps my miner was stuck in a lower difficulty pool?  It seems to affect the miner that was mining at a difficulty of 256 a lot more than the one mining at a difficulty of 90.