Could be the start of anthracnose, this is a photo (not mine) of an infected inflorescence:

There are other fungal diseases as well and it might be one of those. Have you had a lot of rain/humid weather lately? If you fertilise a lot in wet weather it can cause flushes of new growth which are more susceptible to disease. Over fertilising mangos should be avoided.

Above flowering buds look a bit kinda dirty. I sprayed copper oxyloride twice within 2 weeks nothing happened. I'm afraid it could have a bit of anthracnose, who knows!!! What do you guys think?

The two first pictures are from a different tree from the remaining two. The buds from the first pics haven't changed color at all even after spraying. That is what worries me.

The color is from spraying micronutrients