Did you hear officially from Duke or Northwestern? I saw the two posts on gradcafe but I don't know if this was an official rejection or an information gained from reaching out to a POI/department.
I've heard the following updates (ALL for micro OB/Management):
Wharton--Sent out all invites "earlier this week"
NYU Stern--Starting to review applications next week
Fuqua--Haven't began reviewing yet
Columbia-- In the "midst" of reviewing