The short answer is yes, dig up the old bulbs or just cut off the foliage to tidy the area and replant fresh bulbs in the fall. Sounds like your original daffodils multiplied and now they are too crowded and small to flower so just send up leaves. Sometimes this happens when the bulbs get water in the summer instead of going dormant by sitting in dry soil. Professional growers dig the bulbs each spring after they flower and ripen and replant every fall. If you leave them in the ground you are gambling that they will develop side bulblets and bloom less. I have found that the tiny or miniature daffodils like the Tete-a-tete or February Gold varieties of daffodils are the most likely to return year after year. Keep growing, Marianne Binetti