What must be the reason and what is remedy of attached photo of Mango tree. The plant is Alphonso tree of 11 years now developed from seed in my home garden.

This is happening 3rd year in row now. Initially the blossom develops nicely then after few days they seem to become dry and look like burnt. Mangoes are not developed. 3 years back it was first year of fruitfulness. Only 1 mango was developed. Next year treated with herbal fungicide during pre blossom and during blossom. Still same problem observed. All the blossom was seen burnt like dry with only 5 mangoes that too not properly developed. This year also treated with herbal fungicide and pesticides and yet the blossom has dried.