yep that makes sense. just never really thought about it, I use Advanced ph down mostly, and it doesn't have an NPK on the bottle. Wife came home with ph down from DG with an NPK on the bottle, im like "uhhh!" ...and it takes a lot more volume. Why don't Advanced or GH put the NPK value on the bottle? is it derived from some other source?
*edit:
you already answered this, so thats crazy as hell! at least with advanced it barely takes any, but some of these take ounces and ounces, wowzer