MG potting soil giving possible ph problems

I planted 5 germed seeds 18 days ago and I have been having slow growth, due to what I believe is a ph problem. I have the seemorebuds book and it talks about how the MG soil has a ph around 5. I have read that elsewhere on these boards as well. I was adjusting the water accordingly assuming that it had a low ph. I finally tested the ph of the soil yesterday and it came to around 7...How could this be? I have thought about buying another bag as its the only thing available around me and adding things to adjust the ph. Currently they are in 3 gallon pots. Would transplanting into more mg soil with an adjusted ph help?

Give them time to grow. Its not like they grow 3 feet tall in 18 days.

Im not being inpatient, some are less than 3 inches tall after being under almost 300w of cfl and 150w of hps (both well focused and very close to the plants). There is no way they should be this small after this much time.

Yea thats right. They have the organic mg soil. Its good. Just add perlite.