Questions about tds and flushing

I"m sorry if this has been covered elsewhere in these forums, but I've read until my eyes are crossed and just got more confused. My tap water has 270 tds. pH of 7.0, If I adjust the pH with vinegar, would the water be OK to start seedlings in? I"m growing A11XC99. I'm thinking I'll use bottled water (TDS OF 17) until the seedlings get a good start, and tap water after that. When they're going good (5or6 in tall), when I water them I'll use 1 gal ph'ed water per 1gal pot, hopefully this will flush out any tds build up in the soil. I tried using MG potting mix, but it had time release nutes in it and I think that's what killed off my first attempt. I used city water in Indianapolis years ago with the same strain and everything was fine. Must have been the time released ferts that burned them, so I'm going with all organic soil this time. What do you think about the tds, flushing and all of that?