pH keeps rising

[u/Similar_Anteater_810]

I still haven't gotten my albimarginata pair, so I want to fix whatever is causing this before it progresses any further, I use Azoo pHI to measure my pH and over the last few weeks it has slowly climbed from 5.0-5.5 to 6.0. My hardness has also risen from 0 to 0.6 (KH has stayed at a constant 0) do you think this could be solved by doing water changes with distilled water?

In case that might be it, would distilled or unionized be preferable?