The test strips will work just fine for a soil grow. You don't have to have your ph DEAD on, MJ will grow and survive just fine in soil with a ph anywhere from about 5.5 - 8.0. This plant is very tolerant, but over time sometimes that ph call fall to 4.5 because of nutrient buildup. It could also be that your water has a ph of like 8.3 (like mine does) and it's jacking you all up. The strips ain' t the best, but they will tell you if you are WAY off base.
If you aren't WAY off base, then I would flush, add back 1/4 strength nutes and use some CalMag (botanicare) to help out. Gradually bring the nutes back up to full strength over the course of a week. You could also use epsom salt to add MG, but if it's a lockout and not a lack of availability you'll end up locking out Calcium and potentially other elements. It's really best to eliminate the ph problem first and give a good flush, you can use CalMag as a foliar feeding to relieve the stress while you sort out the lockout problems in the root zone.
As far as where to get ph up/down you can order it online from all sorts of hydro stores. You can use the aquarium stuff, but it's byproduct is going to be salt so be very careful and don't overdo it.
GL, remember eliminate and identify the problem, THEN react. Sometimes the correction is worse than the original problem.
