Candida will make a white-coated tongue, & would be a common inhabitor of the mouth. Maybe your immune system/liver is just recovering from the flush for a day or so, so it isn't fighting off the baddies as well as it normally does. Just a guess.
If it's candida, I've found scrubbing the tongue with listerine is easier/quicker than the other things I've tried, or you could try a natural anti-fungal like diluted tea tree oil.