Black tongue coating

Of course there are all the TCM reasons for a black tongue described on this site and in texts. But from the western side of things you should check if the patient is taking large amount of iron and/or taking something like pepto bismal - either of which will cause the black fur on the tongue.

To help further on the TCM side I would have to know a lot more about their health - everyone has issues from a TCM perspective to lock onto regardless of their overall state of "health" from their perspective.