Very Bad Lag from ~20 Large Particles

I have a single particle system in one of my levels that emits 2 particles per second with a lifetime of 20 seconds.

The particles are very large hexagons rendered with emission lighting in URP. I have a screenshot below:

There are only ~20 particles on the screen at any one time, so I am surprised that I get massive framerate drops. Is it due to the fact that the particles are 'big'? Is there a work around for this? I really like the visual I have created, but there's no way I can keep it if it remains this laggy.

Thanks!