disappeared Half Moons on fingernails

If you do an image search for "fingernails," then about half of the pictures don't involve moons. I'm sure fingernail symptoms of various kinds matter, but there's also some healthy variation. Iron deficiency and general malnutrition can cause nail changes, too, so if you're certain that you used to have lunulae, then I'd start with checking for nutrient deficiencies. My nails have more vertical ridges than they used to, which I have not figured out yet.