Are you cleansing the body for parasites? If so, ask Fledgling on the Ask Humaworm forum. I have read about strange discolorings on the tongue during a cleansing. I do recall reading about a tongue turning black.
It was Terry Lee not Fledgling that had a sore tongue and burning.
Here is a link I found that may be of help.
again it mentions zylitol,gluten free diet,aloe vera, black tea bags on tongue and a special diet.
Someone also mentioned probiotics and parasite cleansing really helped.
You didn't mention if the rings were painful or not.
It seems that geographic tongue is likely so you may be dealing with a malladsorbtion problem. When your small intestine can't adsorb the nutrients, vitamin, minerals you need then you need to find out why this is happening. It's good to consult a Dr to find out more about intestinal problems, a gastroenterologist specializes in intestinal problems. If you do a search for 'maladsorption syndrome' you will see that there are many causes and parasites are among the causes. It is best to have the tests to rule out gluten sensitivies, especially Celiac Disease. People who have undiagnosed Celiac Disease often develop white plaque on their tongue and have painful mouth ulcers called canker sores. The maladsorbtion problem in Celiac Disease is called non-tropical sprue. Tropical sprue is thought to be caused by a protozoan parasites.
Some people are malnourished because they have a poor diet. People who don't eat meat or anything from animals often need to take B vitamin supplements.