White tongue is most likely caused by the actions of your cells spilling toxins which can originate all the way up from the liver. Candida will generally build a plaque on the tongue, which can be scraped off. If you get a bad taste in mouth, it is the high levels of nitrites \ nitrates from the cell membrane attack complexes, being dispensed by defense mechanisms of cells. Then, there are bacteria which are attracted to the area, to feast on the chemicals, which can sometimes result in nitric acid production. This can leave slight patterns on the tongue. Shroom