What are some possible reasons my fingernails are flattening out on the ends? there has been no trauma to them.

Flattened nails: Flattening of the nails at the ends could be koilonychia (spoon nails), most commonly associated w iron deficiency anemia. Other conditions with spoon nails, like trauma, hemochromatosis (iron overload), raynaud’s, lupus and nail-patella syndrome. Please see your dermatologist for an evaluation. Since both too little and too much iron can cause this, don't start iron before testing for it.