Sorry, wife got up early so had to do my chores, lol. (I forgot to answer your flushing question)

I flush monthly with a 1:1 ratio, if necessary. (one gallon of properly ph'd water per gallon of pot size) to release built-up nutes and salts. If plants are looking fine with growth and color, I'll just add a gallon of ph'd water to a 3 gallon pot for these monthly flushes.
Then, I'll do a final flush between 3 days to a week (at the most) before harvest, and I flush a bit more aggressively. Like 1.5:1 or 2:1.
Plain, ph'd water till harvest. (if necessary after the flush)

What's your tapwater ph? If within ph range, usually tapwater is fine, but municipal water usually has chlorine, so sitting it out overnight is recommended. (the chlorine evaporates) Rain water is full of contaminates and tends to be too acidic without adjusting. (Acid rain)

I feed twice weekly with a half-strength solution of my Fox Farms nutes. This drops my ph by .1 or so. A full-strength solution of FF drops the ph by around .2 ph points. Your nutes may vary in ph and bufferers.