I'm not a fan of Hanna, and my local hydro shop doesn't even stock them (the Oakton pH and Truncheon EC are apparently the best bang for your growroom buck as far as they are concerned).

6.5 is not too low for soil or soilless, but definitely keep an eye on it in case it gets any lower. I'm surprised that your distilled water measures at 7.0- generally, the presence of dissolved atmospheric gases (sepcifically CO2 and N2) will actually drop 'pure' water down into the 6's. You might want to get a 'second opinion' on your test kit!

Remember, for soil grows, tap water is perfectly acceptable in most cases!