Early potatoes? Did they get hilled and did they get enough water after they got about 3' tall especially if they bloomed? They can also die back early due to stress. Without pictures it is hard to tell. Dig into one of the hills and see what size the potatoes are. If they are big enough to eat just eat them. Don't use any for seed potatoes to be safe and in general that isn't a good idea to save your own potatoes for seed. Some do with heirlooms, but they generally know what to look for.