Like i said nutrients will lower your ph levels in your dirt. I only give my plants nutrients once a week. I water them twice a week. When i juice i let a bit of run-off maybe 5 %. When i water i basicly flush them. It balances them out. Because your flushing all those acidic salts out of the medium. Out with the old and in with the new.
Works great for me and i use the same promix as you.
Depends on the person. Lime does work to buffer but can also cause some problems if used to generously.
Check your run off ph.