How do you actually 3 star even the first one? I keep getting the biggest souls you can and tossing them in, yet this way it's not possible to get the 3 star clear it seems. The physics of throwing seem to be a bit off as well; sometimes the balls just refuse to leave the pot.
EDIT: Okay, so now I got the gist of this. It's all down to luck; if the little cauldron doesn't give you bigger souls all the time, you cannot get 3 stars. If you play this game, just forget about trying; throw balls in as they come and hope you get the bigger scoring ones.