Here's what happened to me with a clone I have - two nights ago I fed and watered it - I tested the run-off and it was like 5!! So I mixed up another batch of plain water, added Ph-Up till it was at 8.8 or so and watered the plant again. When I retested, the run-off was 6.5 - right where I wanted it.

I dunno if that is how it's supposed to be done but that's how I'm stumbling along with it.