1. Varietal differences: Some varieties of Kousa dogwood naturally produce pink flowers instead of the typical white flowers. It is possible that you have a variety that produces pink flowers.
2. Environmental factors: The color of the flowers can sometimes be influenced by environmental factors such as the soil pH, nutrient levels, and sunlight exposure. Changes in these factors can sometimes cause the flowers to turn pink.
3. Stress: If the tree is under stress due to factors such as drought, disease, or pests, it may produce pink flowers as a response to the stress.
4. Genetic mutation: Sometimes, genetic mutations can cause plants to produce flowers in different colors than usual. It is possible that your Kousa dogwood has undergone a genetic mutation that has resulted in pink flowers.
Overall, pink flowers on a Kousa dogwood are not necessarily a cause for concern and can simply be a natural variation in the plant's coloration.