Rapid ph change ,help please

hello folks, for the last week iv bn having rapid ph changes in my 5gal buckets, because of this i have to adjust my ph 5 or 6 times daily. Last night i did a complet flush and change. i got 6gal of distilled water added my foxfarm nutes a little LESS than half strenght, and ad big bud(1st) let settle for an hour and the ph was at 2.6, then i adjusted up to 5.9. rite b4 i went to bed. wen i check them again a few hrs later they where at around 7, could this b because my nuts strenght is to low. im in my 3rd week of flowering and im having trouble keepin my ph in range.temps in my room are about 78-80 with the lights on. i can i possibly keep my ph in range for at least a day. Oh yea i dnt have an tds/ec meter. Could i use peroxide to the help my roots the look a little brown.

a few of my fan leaves are turning dark brown and crispy at the edges. i dnt know if this from over fert of or nute lockout due to my ph being outta range. But i never put my nuts no more than have strength. 2 5gal buckets, 3gal of water a peice

What are your water temps? Sounds like bacteria...I would definitely get a tds meter. You can find the online for 15-20 bucks. Are your buckets light proof? Do you have a res? Are your buckets connected or stand alone units? Sounds like nute burn too. How old are your plants? Young plants wont need nutes right away and I would have started them at 1/4 strength.

if your in your 3rd week of flower and it just started doing this did you do something differant than you were doing,add something maybe?your sure there is no light leaking in your bucket,have you changed out you nute soloution on a regular basis,double check your meter,also check your roots and make sure theres no slime in there,if your roots are slimey you got root rot. good luck