I recently brewed a batch of Northern Brewers Partial Mash Oatmeal Stout and I seemed to have a very high final gravity read of 1.020 with a original gravity of 1.049. I used the Wyeast London Ale III strain and made a 1L starter with it. The Wyeast smack pack did arrive a bit inflated however but I created the starter shortly after the yeast arrived. I also aerated the wort pretty vigorously for about 2 minutes. Anybody have an idea of what could have caused this high final gravity? My krausen seemed a bit thin compared to other batches. I’m wondering if the ambient heat during the shipment of the yeast had an effect? Anything I can do to lower it down?