Did you aerate your wort well? (more oxygen at the start = more yeast activity?
Did your second batch cool down much faster than your first batch after you pitched your yeast? Microbe activity increases exponentially with temperature, which is why the colder your wort the longer it takes to become beer. (or did you pitch too hot, which can kill yeast cells and cause a delayed start?)
It could be either of those, though my guess would be that it has to do with temperature, because a cooler temperature would also explain why your beer is more cloudy.