It means that your nails are dehydrated from overexposure to water and detergents. Do some hot oil treatments of them with extra virgin olive oil, always wear rubber gloves to protect them when you're going to be putting your hands in water, rub a few drops of olive oil into your nails after washing your hands (every time) and stop worrying about your stomach acids, which have nothing to do with it. You're making a simple matter far too complicated. Most people wash their hands far too frequently with harsh detergents masquerading as "handwash" or do the dishes without gloves and then wonder why their nails are curling under! Water is BAD for fingernails and detergents are WORSE.