SOS: Yellowing leaves

[Holographic_spew]

How do you know your water pH without a means to test? if you're using distilled water, it has zero buffering (the ability to keep ph from wild swings) and no minerals (which for the most part are actually beneficial for your plants). Normally you want to test your pH AFTER you add the nutrients (as these can drastically change the pH). What is your water source?

That post was a reply referring to PPM which I don't have a tester for, I have a pH reader which I use to test the water before and after nutrients, I have a rain water tank that we clean during its empty period :)