BE VERY CAREFUL ADDING N TO MG SOIL. Plants look good dude... doesnt seem to me like there "Asking" For anything ya know? If it isnt broke dont fix it. I spent years spending money on all kinds a shit...still have the bottles with 50$ price tags to prove it, Want em? I wouldnt go adding anything you havent already been doing to these girls when they look so happy with what you have.
In the future, if you really do commit to a change, Ive heard of people having excellent results with a bag of super soil or black gold or the like, from home depot, some perlite for drainage and osmocote fertilizer, not much more than a bag of MG in $ spent and alot more forgiving than MG on babies (Although you seem to have done just fine). Your hps going out at the early stages of flower is a blessing in disguise, with temps at 86* with the lights on and the huge change in spectrum you were looking at a substantial stretch over the next few weeks, by flowering under the blue spectrum for the first bit you should be able to control that better while giving a bit more density to your final product, at least until your ballast arrives. To flush in MG I would pour one gallon of de chlorinated out of range ph water through my medium for every gallon of medium my containers hold. What that means is take 8-10 gallons of water and let it sit out over night (to de chlorinate 3 gallons of run off for each 3 gallon container and a bit extra if needed) then your going to need to ph that water to 7.5.(You will need small container of ph up and cheap ph test shaker bottle, both can be acquired for about the same price as a bottle of the newest and most improve bottle of dextrose flushing agent there selling at the shop for 15$!) Why do I need to ph my water so high you ask? By pouring ph water that is out of range it makes the fertlizer N-P-K and trace minerals in the soil unusable to the plant (which is why you would never normally use this ph level) while at the same time washing said unused fertilizer out of the medium. The plant having nothing to draw on but its stored energy will use the necessary N-P-K it has stored up in its cells (You will start to see sign of deficiencies and curling of leaves THIS IS GOOD) Do this everyday for roughly 7-10 days before the chop and the plant will have used all the N-P-K and mg and trace minerals that would give you that harsh taste to save it self, leaving you a smooth final product. Keep it up all is well. -S0uP