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None of those dates coincide with Panda or Penguin.  And yes, a Panda or Penguin related drop would happen immediately coinciding with that day.  However, sometimes there can be a drop that gradually follows a Penguin or Panda day if sites that are linking to you have been affected.  I'm guessing this is not the case for you though. It's really hard to say what to work on because you still don't know the cause for your traffic drop.  At this point it really would be just a guess.  It's never wrong to work on making unique product descriptions so that may be a place to start, but again without knowing the cause, there's no way of saying for sure that that is going to help.