This is a hydro grow isn't it? ("halo dripper"). If so, get your ph to 5.5 and let it drift slowly up to no more than 6.2. If not, my apoligies, high 6's is perfect.

Pure ro water has no Potential of Hydrogen but the ph will change when exposed to air and not only will you get false readings with a ph pen it will damage the probe. Thats why a little ph up or down goes along way compared to tap.

Your tap water as it is will cause problems.

Subzero.
subzero Reviewed by subzero on . Water & Nutrient Probs Hey guys, I have recently had a few different issues, firstly the leafs were going yellow and the tips curling. I narrowed that down to the water in the reservoir evaporating and the nutrients remaining and being a little strong for the little fellas (young clones under a 600wHPS). To fix this problem i changed the water to plain tap water and let this go through the system (halo drip) overnight. Hopefully this cures this problem. Today i checked the ph of the water and its a shockingly Rating: 5