Álvaro Coes

Hi friends, i'm kinda stuck with this shot right here, i'm looking for a dust off simulation basically for which i've used field forces to push the grains out of the object i wanna show. Since i'm terrible at explaining myself i'll show you guys a first render in the link so you can get the idea.
I was somehow happy with the results, i could fix the crazy grain issue going on in the first render, but somebody told me the grains were too big, they looked like beans haha. So now i'm trying to redo the simulation with smaller grains (from 0.005 to 0.002)
For you guys to understand the workflow, i'm using vellum grain, first I do a basic simulation in which i only let a box of spheres fall to the ground, and from that sim i start another sim to make the reveal effect.
So right to the point, my question is, why are the grain dissapearing in the first frames? It looks like they're shrinking themselves, i made sure i set the velocity to 0 before the sim starts so there's nothing affecting it in the first frame.