this is my first in-door grow. so i have a 2 gallon water jug, that i fill with tape water, let it sit 24 hours, then check the ph, it's about 8, so i add vinegar, wait about 30 mins, and recheck the ph. when it's at 6.5, I water. but when i water two days later, the ph is back over 8, so i have...