ph unstable

alright guys first grow in hydro done many soil and out door grows but im at a loss for this shit i have 9 gal dwc set up and have been using gh bloom and veg and micro for nutes got my ph to like 5.9 with viniger but every day it seems to get back up to like 7.0 to 7.8 thought once i used the vin it would at least stay stable for a lil bit what can i do to get it stable with out spending more cash got backing saoda and viniger witch gets it to were it needes to be but keeps going up like i said never done hydro hope im not fing up all my soil grows were fine lol please anyhelp would help

How are you testing ph?

I would begin by spending a few bucks for ph up & down. Homemade remedies can be unstable. I was told that vinegar can negatively affect nutes. I have used baking soda in the past and wound up with gunk in my res. I concluded that it was not mixing well with something. If your water is high, get the ph down. Best wishes.

Yes, invest in the proper pH control. I tried using vinegar but like you experienced, the pH doesn't stay low for long.

using anything that the main ingredient starts with sodium is bad. baking soda will give salt build up. PH up and down for hydroponics is different than pools it doesn't have the salt buildups and it has stabalizers in it to help slow the ups and downs. I wouldn't qiote this as it's just an assumption but from my experience as the plant uptakes N in vege stage it tends to make the PH go slowly down. As it enters flowering and is taking up more P it tends to go up. If anyone could prove or disprove my assumption I would surley +rep ya