Really strange.  I left it running on three cylinders overnight.   At some point, it completely quit hashing.   I restarted it this morning and now it's running on all four blades.   The blade that was running at 1.8ths before, is now running at 220ghs.   Not the full 256, but I'm happy.

I notice that the temperature is higher than the other three, so there might be a clue there.

Can anyone explain the (solo) temperatures listed for each blade?   The sick blade consistently has a very high number (around 88) in the list of temperatures.   The average is also higher than the other three.   Any ideas as to why this is happening?