I would suspect these are all related. I would suspect they are going through the emails of all top brass first and will work their way down the chain of command as they continue to whack at the Army machine. I suspect this has more to do with loyalties more than anything else. These generals are toast if they've scrived any defamatory remarks or actions against the POTUS.
It would appear Benghazi was a Honeytrap that pissed the Army Brass off and drew them out through discoverable communications. These Generals had had it, and they spilled their guts on emails. Now they're being hunted like dogs, is my guess.