hi ,ive just put a coopers stout down with brew enhancer 2 and the standard yeast.it started bubbling straight away ,but after 4 hours it still wont bubble more than once every 5 minutes, did i do something wrong or is this normal.my previous coopers brews have all started brewing very vigourously within 2 hours, so i figured the yeast might be half dead or something. would i have got better results using the yeast out of a pale ale for this brew. B)