Why do I see moisture coming from the middle of the wing as well as wingtip vortices?
They are vortices coming from the flap panel, same as the vortices coming from the wing tip, but much more intense because the angle to the flow is so high.  Because of this, the pressure drop in the core of the flap vortice much more than pressure drop in the flow off the wing tip. This means the temperature drop is also much more, enough to condense the humidity in the air, like a horizontal tornado.