Please don't spread FUD that there are ASICs for Lyra2z which has already been stated as a transition algorithm. I'll be very surprised if there is
Again, just because it doesn't make economical sense to you, doesn't mean it doesn't make economic sense for others. Lyra2z is a very cool algorithm, which consumes very little power due to its use of shared memory. You can see this when running it yourself and noting how much power it is drawing and also the temperatures. Nvidia cards have an advantage at the moment and having mined it myself, there are times when it's the most profitable coin to mine on Nvidia even when not factoring in the electricity savings. We have been aware of private Chinese Nvidia farms in the past mining Zcoin on their own private pool.
Not for us to question why. There are many other possible reasons besides 'botnets' or 'ASICS' as to the reason of the fluctuating hashrate. Ever consider the cloud mining credits miners?
This is more a result of the BRNDF difficulty retarget function that we use which looks back almost one week of blocks. It adjusts every 6 blocks but it looks very far back meaning that in cases where hashrate is fluctuating greatly, the immediate difficulty adjustments may seem weird.