It's unusual for ferts to make the pH go up. It's not unusual for ferts to make the pH drop back down some after adjusting but going back up is more likely from your pH up. It is more likely that you may have not given the pH up long enough to stabilize before you checked it the first time. What may have happened is that your ferts made the pH drop, so you added pH up and checked the PH too soon, before the pH up had a chance to stabilize. So, when you checked it the second time, it was still going up from original pH adjustment. I have heard you can check pH in as little as two hours after adjusting. But, I have had experience that indicates 24 hrs is a much better amount of time to allow for stabilization.
A couple things that have helped me, is that
I bubble my water 24/7. You can get an aquarium bubbler at any pet store and they can be gotten for less than $20. I also got an extra tank, just for ferts. I use a 5 gal igloo for ferts, which has worked for my size grow. But, I also have a 25gal rubbermaid storage container that I keep about 15gals of bubbled, pH'd water in. That way, I don't have to worry about trying to pH the fert mix over a three day period... that puts too much wear and tear on my peace.
Since I add ferts every other watering, as suggested by Fox Farm, I only need them about once a week. So, I let the water bubble for 24 hrs+ to eliminate chlorine. Then, I add ferts and let them bubble for 24 hrs+. This gives the ferts and water a chance to stabilize well. Next, I take a pH reading. If I already know about how much pH up or down to add, I add it and let it bubble another 24+ hrs. I take another pH reading, and adjust if necessary. If you don't already know about how much to add, it helps to keep a log of how much pH movement you get by adding pH up/down in different amounts to different volumes. I use a dropper when doing a gallon at a time. One drop of pH up or down will move my pH around .1 (i.e. from 7.0-7.1)
At this point you have a few minutes a day, for three days, invested. So, you've still got four days left, and you should have the pH pretty close at this point. Most importantly, you're not working/worrying yourself to death. Just let it bubble until a couple days before you are gonna add ferts to the plants, and give the pH one last look. If it needs adjustment, try to put just enough pH up to get it to the 6.3-6.8 range.
I hope this helps.
