Ph fluctuation 6 -》 4.2 in 12 hours

Sounds like your nutes aren't buffered very well. I'd try a different product if it can swing like that. If you have no light leaks or other practices causing excessive microbial growth, that shouldn't happen so easily. a well-buffered product will not swing so easily under any normal conditions. if you think there are extenuating circumstances causing microbial growth, then that could be beyond the limits of a well-buffered set of fertilizers. clean the rez, look for any light leak or even transluscent bits... probably growing something that is excreting acidic byproducts and possibly leeching some of your nutes. jacks would work great for you... if available nearby, can buy in bulk and pay just under 4 cents per gallon mixed (total for all 3 parts). pH will never be a problem with their '5-12-26 Part A hydro' product. can buy generic cal-nitrate and foodgrade epsom to complete formula. this stuff is like generic prescriptions... a rose is a rose... don't overpay for fertilizer.. it's cheap AF and it's the same exact molecules no matter which brand it is. What can be drastically different between brands is soemthing like buffering that takes a certain understading of chemistry or work experience etc... i.e. a more professional brand employing real proffessionals to make their products.. not cousin billy and nephew steve while they slap a big cartoon graphic on teh label like it's some sort of sugary cereal targetted at children. bwahahah (i didn't look at what you used on purpose... this is hypothetical / generalized and a little humor at the end)