Ph in soil run-off is 8.0 but watering with 5.9

Good morning ladies and gents. This is my first grow I'm in my 4th week of veg but from the beginning I've been having really slow growth with here and there growth spurts, some plants flourishing others not. The last two weeks I've been Ph testing to make sure to keep levels between 5.6 and 6.6. Today I watered and tested my sun off and it tested 8.0 my question is how is this possible and how do I remedy it.
Green crack
vegging 27 days from transplanting clones
1000 watt hps tallest plant just hit 12" smallest 9"

water with phd water on your next watering. you can get ph up or down at your local grow store. it could be something in your soil upping your ph everytime you water, could be that you are running straight tap water, quite a bit of variables sir, also ive found my plants don't veg as well under the hps as they do a mh, t5 or cfl in that order.

Buy some distilled water in the mean time and water real good.
Wait till they need it though.