You want your soil pH right around 6.7.
I think N is locked out by low pH. I've seen this before, in peat mix, pH=very low.
What I am seeing is a sudden nitrogen deficiency- new growht only- which means that yes, something has changed, and I'd look to your new tap water as the culprit. I think you are locked out. Make sure the fertilizer/water solution you are using is between 6.5 and 6.8, do a foliar feed with a micronutrient solution with a drop of superthrive added to start correcting that def right away, and flush your soil really well- then check runoff pH, adjust if necessary, and feed with a dilute complete fert.