Well if it doesnt have mixing via water instructions, then I believe your nutrients are suppose to be mixed into your soil at the measurements requested. See my nutes require to be mixed with the water, not sure how yours are? Chemical nutrients are just unnatural nutrients. I've seen them grow very fast and potent buds, however, most people prefer organic, because chemical nutrients are just very unhealthy and unnatural. Ya they get the job done, but your putting this stuff in your lungs, who knows what kind of long term effects using chems would/could cause? I personally reside with organics mainly because I love the pure taste of the smoke. not to mention I am a medical grower and cargiver, so I have to have the most natural/healthiest flowers possible.
Ive noticed with chemical nutes, it all taste the damn same... Whether you flush or not.. LoL! However, this is just my experience. You should use either or, organic nutes, or chemical nutes.
As for your leaves, when flowering, yellowing leaves is normal. The bud is using up the nutrients within the leaves and they start to yellow and fall. However, yes depending at what stage and how far along it is, you should add more nutrients. Usually the instructions will be for for full strength nutrients. Then what you do is cut it in half or 1/4th, etc. you dont want to put full strength right away. However, at this point you might be fine putting half to full strength if not already. With that said, this is really hard to help you with, as Ive never used nutrients that didnt have instructions for water mixing. Thus, I have no idea if these are even proper nutrients? Sounds to me like you just might be feeding it some beneficial microbe nutrients, which is good, but you need a whole formula mix, like Fox farm Nute line, or Bio Biz nute line, or General Hydroponics nute line, etc. Is it possible for you to post a picture of your nutrients so I can research and what exactly it is?