6-7-12 is fine. at 8g per gallon (if it were dry nutes .. i don't want to assume lableling methods, but 8mL/gal should calculate the same as long as it isn't listed as "W%/W") this results in a ppm of 127 / 65 / 211 -- the K might be slightly high which could be impeding other nutes.
i have used a very similar ratio of npk and my plants look healthy seed to harvest with no major symptoms of deficiency nor toxicity.. so the nutrients are not the limiting factor for growth, which is all we can do in regard to feeding a plant. you can't force feed it like it's foie gras. giving more and causing buildups in leaves doesn't make your buds fatter, lol. that's a bunch of hubris related to one's own decisions being ultra important and meaningful with absolutely no comparison to a control group to protect the ego.
Ca/Mg/S and micros all hav a say in that too... not only is concentration imortant but ratios of each molecule are equally important.
i see a lot of questions about biobizz the last 3-4 months.. the plants often look fucked up, lol. so, either shit products, porr instructions, or ppl use it wrong (any combination of the three too). Maybe their coco isn't washed or buffered well? but, if that's the case you'd see issue from day 1.
One other thing.. since runoff pH is lower, that means the substrate is probable lower than the runoff between irrigations -- at some point. this could easily throw a wrench into the best ratio/concentration which is relative to other factors like co2, temps, intensity of light et al