I have heard of kelp as a good foliar spray like someone a couple pages back did, also canna makes their bio boost which is used as a foliar in the beginning of flowering, can prob do a soil drench but hear most of foliar *I do not use this or endorse this just saying its out there*. I have only tried foliar feeding with tap water, have not had a prob and they seem to like it, no dish soap either, shocker I know lol. Oh and HG makes their magic green foliar feed which I have good things about as well, but do not think its organic if that is your thing.
EDIT: Pretty sure the spraying at night with hids is so you do not shatter your bulbs with a drop of moisture, just my thoughts though, I use LEDs

.
