When the missiles explode, I instantiate a bunch of lights and meshes, and after a while there's TONS of lights and meshes, and that seemed to cause some problems. I'm not very experienced with Bevy but I took this as an opportunity to learn a lot. Thanks for the tips, I have around 3-5 laptops of varying performance that I use for development (and my workstation which is quite powerful) so I usually get a good breadth of machines to test on.
I did remove some lights etc to get better performance, but in the end... yeah, it is what it is.