Not sure if it makes it stable, but it DOES raise it.
I bought some concentrated PH down, one teaspoon will lower my 18 gl reservoir from a 7 to a 5. UNLESS I make this mistake again. I lower the PH first then added the nutes, my PH went way down, 4.7 so I added baking soda to bring it up. I made this mistake twice now, then I have to add two teaspoon of PF down every day to maintain the PH to around 5.9.