Anyone know why Wei Ying got nose bleeding and fainted in episode 46 while he visited the Lotus Cove?

It's where all get to know that Wei Ying gave his golden core to his brother.

Was ist from the fighting before? Because he was fine a while and fainted then out of the blue.

Putting under spoiler just in case :)

Yes, he fainted from expending the energy in the fight at the Burial Grounds. The sudden provocation with his brother (and I suspect being at odds with his own golden core) resulted in him passing out. Hope this helped! 

I was suprised because it happend so fast that I wondered first, but I had the same thought. :)