Brown top leads to splitting and rot

[Lukasrl]

Hello everyone,

One of my friends came to me asking about a issue he is having with one of his tomato plants. He has a Big Zac tomato plant and he said that his tomatoes will be fine but they all have (Ok before you read further, not blossom end rot) brown spot on the crown of tomato. Not the bottom. He said this leads to cracks in the tomato and then they rot while they are still green.

I have never seen the brown tops before. But either way with the cracking I would think its because of overwatering. But even with over watering, i have never had green tomatoes crack.

Cant seem to find the brown tops on a google search. Let me know what you think.