Displacing a tracer

[signature-view]

Hey, I'm trying to create an effect where a tracer traces the vertices of an object and those traced paths become flared out over time. Essentially I want the tracer to start out small (and attached to the traced object) but then widen out at its ends. I've tried using a tracer with a gradient shader set to spherical. That's the closest I can get, but if you look in the top view you'll see that the effect is scaling from the centre of the scene, not the centre of each traced object. Am I missing something super obvious here?

thanks