Transparency on mesh drawing over coloured pixels

For the dynamic clouds I'm making, I need a bunch of billboard quads. As this number can reach the thousands, I've put them all in one mesh and wrote an hlsl vertex shader to get the billboard effec. The problem comes in when trying to use a texture with transparency in it.

After looking online, I think this has to do with the depth pre-pass, but I couldn't find and method of resolving this. If anyone has any thoughs on how to fix this, or a better method to achieve this result, I would love your advice!

Ps. while I am currently using the default 3D pipeline and so would prefer non shaderlab or hdrp solutions, if its a fix I'll take anything at this point.