smh
i can't post a url without being filtered... simply google image search - plant avilaibilty ph marijuana - and you can verify that lower pH does not improve N intake. that's overtly not true for all plants, not just marijuana.
you can see that lowering ph does not increas N availibility to the plant. in fact, the exact opposite occurs. You can also see why a pH lower than 6 is just stupid. Despite cultural beliefs, the medium you use does not affect the chemistry of the plant. once the water goes in it doens't matter if it was contained in soil, soilless, or just hydro reservoir. To think differently would be absolutely in denial of reality. it happens because ppl did it once, made it work, and their ego immediately jumps to "this is the way" lol..
but it isn't. availability in the plant has nothign to do with the substrate in regard to pH.
the suggestsion fo 5,8 for hydro is silly and misguided. all it does is force those to use more N, P, K, Ca, Mg, S to make up for the sub-optimal availability caused by a less than optimal pH. it 'can' work.. but it's not 'better' just bc culture says say. that's faux-science.
the ppl proclaimingn it have never tested the hypothesis but have 100% confidence in it.. that's called "faith" not science. might as well pray for your plants too.
you were given bad info here. i'm sorry i was a dick about it, but so much bad info has been given in the answers lately. i feel sorry for the ppl taking advice this month. they'll be even more confused going forward.