Ph advice ...

I have an Oakton PH tester.I have calibrated it with a 4 and 7 buffer solution.Water that I have left out for 3 days is at 8.2 ... Water right out of my tap is at 7.1 ... Filtered water ( Britta filter ) is at 6.7 ... Anybody know why there is such a difference in the readings ? What is a good product to knock down the alkaline in my water ? and what are some symptoms of high alkaline water ? ...

I use general hydroponics PH down

you can lower by adding some freshly squeezed lemon in the mean time that you get ph up and ph down or just the one you need. As for symptoms, its easier if you name whats going on with your plant instead of making us name all of the symptoms.