Nails/hair are brittle too. gums thinned &rims have lightened/few upper teeth have white spots& teeth turning a faint tan color. no cavities/perio?

Systemic disease: It sounds like you may have something that may be more than a tooth problem. I would suggest seeing a physician and possibly a dentist who specializes in oral medicine for an evaluation.

Sepreate problems: You ought to consider visiting you dds for your tooth and gum questions and your md for brittle hair and nails. Your adult are done growing and the outside appearence of them are usually not altered by a systemic conditon unless there is vomiting or severe gastric regurgitation. If your teeth and gums have no pain there may be no problems. Get them checked anyway if things have changed recently.