Parasite cleanse, Candida cleanse and also liver flushing makes you acidic for a while. It's caused by the toxins flushed out (liver flush) or the toxins which are released from dying microorganisms. When I'm on a cleanse, or after a liver flush, I have very bad back pain and also pain in fingers, shoulder and so on.
What helped me: much water to drink, sometimes intake of magnesium/potassium (cleanses consume a lot of minerals). In heavy cases I take a bit of sodium bicarbonate in a glass of water (but wait with meals about half an hour after taking it, because the sodium bicarbonate neutralizes the stomach acid, which is important for a good digestion). Making a plain enema can help, too.