Does Hamilton draw water from lake Taupo? We here have had some messing around by the TDC (water) and also KH here is 0-2 which can contribute to Ph swings.
How long has the tank been running?What fish do you have?What else do you have in the tank?What size tank?What manner are your water changes?PH from tap?
NZCOURIERS charge $29.80 for every 5kg / .025cu m whichever is the greater.(cash sale) If you know someone with an account it is about $25. COURIER POST charge about the same. POST HASTE is a 2 day service. FASTWAY are a lot cheaper on small packages but I am not sure about delivery timeframe. PETER BAKER TRANSPORT I have no idea.
NZ water in most areas is around 7.2ph so I would forget the ph up/down if your tap water is around the same, daily water changes are a must and you may have to treat the white spot again. Raise the temp to a minimum of 19C to help combat the whitespot.
lymphocystis is incurable and it has to be cut out according to my information,it is transmitted through burst cells and it causes the skin cells to grow abnormally large.(easily seen with the naked eye.)
6ph is 100 x more acidic than 7 which is the preferred ph for danios so my opinion is yes this is your problem. The pinkness will be acid burn. You need to find cause of ph drop. How long has the tank been set up and how often do you do water changes?