A couple things before I wisk my wife to the airport...

Is Farfrds Red a time release soil, or the regular potting mix? Adding full-strength nutes can cause problems, if the soil already has nutes.

Adding garden lime to pots...I always run some water through prior to adding the plant. This way, the lime can interact with (melt into) the soil...not the roots. (can burn the roots with direct exposure)

Unless I'm correcting a major problem, I usually flush with the volume of the pot. Not three times the volume. Three times the volume is kinda overkill for a simple flush to remove salts/nutes. If your garden has proper drainage, switching nutes is unnecessary. (thought you were talking indoors, though)

What method of testing runoff are you using? If one of those color-coded test kits or a soil probe...your results will fluctuate wildly. The color coded test kit is skewed by the color of the runoff, and the soil probes never work right. Ever.
If using fresh potting soil, and an ingoing water ph of 6.6, worst your runoff ph should be is 6.2 to 6.4ish. (approximate) Adjusting water to 7.0, and adding limestone dust (garden lime) might be bringing the ph too high.