I'm not a fan of the Earth Juice pH stuff. I tried it and it didn't work for me. I use the AN pH gear. It's highly concentrated, so it takes very little, and stabilizes quickly.
Studying your thread you're basically in a mix of Subs super soil and edna's potting mix with the majority of the mix being edna's? There could be a reaction going on between the two mixes dropping the pH. Hard to say what exactly the cause is without all the information.
What kind of mix are you transplanting to? I will add this again, consider adding dolomite lime. It doesn't take a lot and a huge bag is pretty cheap and usually available at larger garden centers. Though possibly not in the off season.When you add dolomite lime to the mix it adds a little cal mag to the mix and also acts as a pH buffer for your soil putting your plants in the correct range to feed on the vast majority of all they need.