pH is a logrithmic scale.. the ... x^10th at each step from previous.
the strength of acid/base varies, so that can impact it too. some more willingly donate or accept that proton (H+)
it's a ratio of resulting H3O+ : OH- .. 10:1 is 6 ph
100:1 is 5pH
1000:1 is 4 pH. (if going other way it's 1 h30+ to 1000 oh- and 10 pH)
it's a balance of the two it the further from 7 the more difficult it is to move the needle, yes.
Do not buy "ph-up" specific chemicals.. simply look at the ingredients used and go buy it at your local supermarket, LOL.. for 1/5th the price.. and molecularly the same goddamn thing.. they are extortionists... most marijuana brand companies charge a premium for ubiquitous items you can find at multiple other sources for much cheaper.
acetic acid is fine... bases.. usualyl don't need a base.. but can use sodium bicarbonate sparingly.. if it's something that needs to be added all the time just find a base that doesn't have Na or something else detrimental with long-term use.
ph-swings are caused by shit-ass products that aren't buffered properly... if pH swings, do not blame the ph-up or ph down used.. that is not the cause.. it's some poorly thought out product that refuses to apply old knowledge from any other sector of agriculture...
in soil it may be self-corrected, so soil-based nutes are not as important to be pH buffered as soilless/hydro... but... if it's swinging that's trash.
imo, it should come out to a proper pH when you mix it... that is easy to do and well-within our specie's capabilities with existing knowledge and technology for the last 100 years or more, bWAHAHA. it's just ignorant ppl spewing commercial product out there hoping ppl don't know any better... the last thing you should think is that marijuana specific products are somehow better for growing marijuana, because for the most part they are not.. it's more of a marketing scheme like the term "organic"....