Diagnosis
Diagnose: Watermelon Poor Fruit Set
Use these observations to decide what to check next.
Count female flowers, not all fallen blossoms
Male watermelon flowers have a slim stem directly behind the petals and naturally drop after releasing pollen. Only a female flower has a fuzzy miniature melon at its base.
If that ovary never enlarges, audit pollination. If it swells and later yellows, inspect heat, water, roots, and vine load.