Welcome JW. None of mine are Dreadnaughts, although my first Taylor was a 1991 510. A picture might go a long way to being able to help you. If you are in a dry climate then I would highly doubt that you are over humidified. A slight bow in the back is common on some “flattop” guitars, but if you just noticed it it must not have been like that for 15 years.
So, maybe a pic, and consult a local luthier unless you have reason to believe it really is over humidified.
Good luck.