Why did the fund Yinfeng fall by 20% on April 2 1?

That's because the net share value of fund B is only a little, and the price of fund B far exceeds the net value.

Discount is to redistribute the holding quantity according to the net value, but the net value has not changed, but the price is reset to the same number as the net value. So, it seems to be a loss. Simply put, the parent fund is a mother with two sons, A and B.