Mango Tree Leaf Burn - No Pests

Hello,

I have around 100 mango trees and i noticed some trees showing leaf burn in April, but now i see almost all plants are showing leaf burn. Based on my research there can be many causes for leaf burn like pests, root rot, salt in soil, nutrient deficiency, too much nutrients etc. I am not sure what is the issue or how to solve this, can anyone advice on this issue?

Please check the pictures.