I piched my wlp 300 at 24.9 c and had fermentation about 8 to 10 hours after that, at that time the temp was at 21 c. I it picked up wery quikly and was bubbeling along very happily, but 40 hours into fermantation it has slowed down considerably and almost stopped i mesured the gravity and it had gone from OG of 1051 to 1030 my goal is 1010. Is this quick drop in fermentation activity normal ? And if not what am i surposed to do.