An inaccurate meter certainly isn't going to help with anything.
With soil you do not have to adjust the pH of irrigation water or fertigation solutions, period (unless someone keeps putting lye or hydrochloric acid in your well). There is really no debating this, if you ask me. If anything, your soil/potting mix needs some garden or dolomitic limestone. Soil resists sudden changes in pH, due to something known as cation exchange capacity (or sometimes buffering capacity). CEC is essentially a measure of how well a soil or media can hold onto nutrient cations (via ionic bonds to soil particles). Many needed plant nutrients are only available as cations, which are positively charged atoms/molecules such as H+ (acidity), K+ (potassium), Ca++, Mg++, NH4+ (ammonium cation), Na+, etc. You can think of the CEC as a pool or a buffer, of both nutrients and acidity.
Humus/clay are the components of soils largely responsible for their CEC, while materials such as coco coir and sphagnum peat moss also have CEC, whereas rockwool, perlite and sand have virtually zero CEC/buffering capacity. This is one of the most important concepts you can understand as a soil/soilless grower.
http://www.spectrumanalytic.com/support/library/ff/CEC_BpH_and_percent_sat.htm