We had a drop in the hash rate for about two weeks. That's why it's taking slightly longer to get the required number of blocks. Then the hash rate went way up. No idea why. Maybe one of the big mining farms was doing an equipment upgrade and shut down for the changeout. The difficulty adjustment tomorrow will probably be 1-2%, much smaller than last time.
I wonder if the drop was when Butterfly labs was shut down by the US government but then given the ok to run limited again. Maybe their server farm was down for that time but is back up now.
It is possible, but it is also possible that it has to do with the price falling as it is potentially not unprofitable to continue to mine at current levels after electric expenses are taken into consideration