A few Questions with pH and soil

Ok so I've been on a roller coaster ride with my grow, I posted it in "plant problems" , but that isn't why I'm posting here. I decided to transplant because I tried every other fix I could think of and noticed immediately the major drop in pH. I used miracle grow soil and before the transplant I had a runoff pH of about 6.5, and after it was at 4.7 ...... I flushed with what seemed like 10gals of higher pH'd water per lady to get into the acceptable range and I was just wondering if this is common for other fellow miracle grow soil users? I went with miracle grow due to it's price, but is there other soil close to the same price with a pH closer to the acceptable range?

The PH level for good growth is pH (7.0), to increase the PH level add some dolomite or pear-lite lime.