How did it take you 4 months to think about the grinder? That should be the first thing you check when your coffee tastes off. Water matters but a bad grind will wreck your cup way faster than tap water ever could. Uneven grounds give you both sour and bitter at the same time, no water fix is saving that. Buying fancy water or a filter is a waste if your grinder is all over the place. Glad you figured it out but man, four months of bad coffee hurts to read.