I've sometimes felt the worst when my pH is up at 7 or more.
I interpret that as being intense on the cleansing front, with a large 'liberation' of minerals, to compensate.
Intereresting too is a pure water fast--in some ways it is a more gentle, though longer, (can be) sometimes deeper adventure! :-) When the body is left alone to scavenge and heal, it does a pretty amazing job of keeping the pH balanced, and the whole system healing. it's actually suporisingly 'easy' once you pass day three-- but that goes form almost any kind of change.
With the herbs and juice, etc. the body is still focussed on digesting, etc. etc. in any case, it's all good.