Flush time!
I don't pump loads of water through each pot any more, now they're sitting on a tray without drainage. I've found feeding non ph'd water in the same amounts I've been giving them throughout still allows them to cannibalise, and also locks out any nutrients immediately now they're being given non ph'd water.
I've done this for long enough to be able to confirm no difference in the overall flush, the taste or smell, or a negative impact on the plants. Personally I find it a waste of time and ph down when the goal is to stop them feeding on the nutrients in the medium, but rather the nutrients stored in the plant.
I always feed only water for 2-3 weeks, never less. ๐ฆ