Does depend how big a bottle you were mixing as to how much a couple ml's of water will affect it. The isolate itself will be totally fine but I would think it would possibly be a little less efficient than normal because of the reduced vaporisation temperature. Water evaporates at 100° as opposed to 190+ like VG and PG does so it will be harsher and you may want to drop the power a bit to account for it (if you're not vaping in TC mode). And yeah shake the crap out of it like SirLugg said.
*Just re-read the post and saw you only put a few drops in a tank, ignore me it will be fine in those quantities.