Alpha blending for pseudo-sprites in direct-x

[xytor]

Hi, I am using direct 3d to create sprites (rectangles with zero thickness). Applying a texture from a picture with alpha seems to work properly (as long as the render state sets alpha blending to true)

However, the problem arises when I try to make the sprites have different z-orders (by adjusting the z values of their vertices in relation to other sprites)
Then the alpha blending goes away. why is this? how do i fix it?

[xytor]

The problem is resolved.
Apparently, they must be rendered in back-to-front order.