Is your tap water from a well or from the city? Soft water that takes a lot of pH down may have other crap in it. Or your meter might be not reading it right. What is the actual ppm, and if you are on a well, what is the surrounding landscape, especially the type of bedrock?

Something is not adding up. Have you tested the straight tap water, before leaving it out, with the liquid drops? Low ionic strength solutions do not register correctly on cheap or failing electrodes.

Chloramine does not evaporate. Neither does bleach (there should never be bleach in your tap water anyway!). Leaving it out to be better for plants is a myth. The only way to get chloramine out is by charcoal filtration, like aq fish tank filter or brita, and it's not necessary. If your water is considered safe to drink, it is safe for plants, although a fully-organic grow might have some issues at high levels of treatment chems.

You only have to check and adjust your pH once, and that is after adding ALL the fertilizers and before giving it to the plants. Quality ferts like Canna actually have a pH buffer in them to bring you to the correct pH if there is not a high level of interfering junk in your tap water.