Can geographic tongue be a vitamin deficiency? If so, which ones are good to take?

Sometimes- B12, Zinc. There is no single cause of geographic tongue- it can have genetic tendencies, be caused by food sensitivities, toxins or imbalances of intestinal flora, but many find that vitamin B12 or zinc help. There is no guarantee these will help but they are safe to try-see http://collectivewizdom.Com/geographictongue-top10causesandcures.Html try B12 as sublingual methylcobalamin, zinc as zinc picolinate.
Possible, not likely. The cause of geographic tongue is unknown but it is a totally benign condition that does not need treatment. Don't worry about geographic tongue. Some vitamin deficiencies can show up the tongue, especially b vitamins, and can also cause burning tongue.