There is a belief by some TCM practitioners that the white tongue coating (and indeed, whenever people talk about 'candida' or candida symptoms) is the result of food not being digested enough, in other words instead of fungal or yeast-caused, it reflects the state of the intestines and basically sluggish digestion. In that case, remedy the GI issues and it should resolve the white tongue (although an ever so slight coating on the tongue shouldn't be a concern).
There is (IMO) definitely a correlation at least in my experience. Looking back, when my symptoms were worst, the tongue coating was the thickest. Now it's reduced considerably but is still present.. many people deal with this so good luck qbfox.