Hello. Our mango tree starts out healthy every year with new leaves and flowers. However come April and May both the leaves and the flowers start whithering and dying. They look unhealthy so I am guessing its afflicted with some disease. I have attached pictures for reference. Would appreciate it if anyoone has any tips on how to prevent this.

I am in Southern California (Zone 9b). The mango tree gets direct sun about 4-6 hours. It's planted in the ground. It's about 5-8 years old. It has never bore any fruits.