It could be any of all three of your suggestions, in my opinion.
I would be less inclined toward #3 though, unless the traffic drop supports a downturn AFTER the reconsideration request was filed.
But if the drop in traffic was prior to the reconsideration request, then I would tend to dismiss #3 as likely.
"Many SEO blogs posted allegations that the "Lenient" message was not an indication of a penalty - simply an automated warning."
Are you familiar with the Jefferson Bible? If so, I think we need to apply it when reading what certain bloggers write about the google algo.
Really, the traffic chart / ranking charts will probably reveal the closest thing to the truth.