Tried brushing with the peppermint essential oil tonight and it worked like a charm. I have now woken up after a long night's sleep and still have a pink tongue, so it seems to have some staying power.
My daughter started taking peppermint oil capsules to aid digestion and noticed the bad taste in her mouth disappeared and tonsil stones stopped forming. When the capsules ran out the stones came back. Restarting the capsules resolved the problem again!!!