reworking DIY SMT board
A photo might help to better answer this, but QFN packages on properly designed footprints, should be self-aligning during reflow, and if they are misaligned it would typically be by an entire pin (1mm could be more than one pin), so it seems something is seriously wrong. This TI application note explains it. 



I would suggest removing the QFNs entirely with hot air, cleaning the pads with fine desoldering braid and trying again from scratch. Just reflowing and moving the QFNs might result in shorting. 

If you've got good control of your reflow process so as to not cause undue damage to the parts already soldered, I think I'd run it through again rather than trying to solder with hot air- QFNs can be a bit finicky. You could shield the board a bit with aluminum foil if there are some parts that don't like the heat (e-caps or connectors, for example), but not too much of the area.