On the Rocket and Star quests you get a mutiplier for every Star or Colour Bomb collected. problem is if like me you have completed ALL existing levels, you can not possibly compete in the quests against other players who potentially have 100's of unplayed levels availlable....
You either need to apply the multiplier to ALL levels regardless of weather you've completed them or not, or require items that can be more easerly obtained like striped or wrapped candys which can be multiplied by combining with a Colour Bomb.
Stars and Colour Bombs are useless when like me you can only get them at 10x less than someone who has plenty of uncompleted levels at their disposal.