PH going up dont know why, with pics of budding scrog

hey guys iv got 2 plants in a recirculating system,
i adjust ph to 5.8 everyday and the next its between 7.5 and 8,
using a proper ph down and it works good, my ph meter is calibrated properly
whats up with this im going thru a 350ml bottle of this ph down every three weeks

now for some pics,
no problems yet but im sure a ph lockout is bound to happen as i cant adjust ph every 4 hours

its actually happening to some dwc aswell,
in new zealand meant to be autum but still geting high temp days, someone said it could be the temp mucking with everything but my resivours are cool

What nutes and water are you using?

using flairform with tap water, keeping ppm around 1100 its good stuff and ph is the last thing i adjust, but even if i dont add any more nutes or water the ph jumps up

I have no experience with flairform. Do you ever clean your rez? I grow DWC style and my ph issues usually account for a dirty system, light leaks, or possibly the nutes you use. Give us a little bit more info on the system. Do you have a float valve to top off the control bucket? Walk us through your feeding and cleaning process if you would.

i dump the whole res every fortnight,
no light leaks to res as its in another room, its also happening to my dwc setup aswell, its like the plant is changing it as sometimes my ppm jumps too, im thinking its drinking more water than nutes