Prefab using same particle System ?

Hi,

I'm instanting some objects and once they have reach some distance, i want them to activate their particle system. Since they are all instantiated from the same prefab, it appears that all their particule system are enabled or stop at the same time, they cannot be enabled separatly.

Does someone have an explanation for this ? I think it's made that way to make less calculation, is there a way to get over it ?

Thanks