My blueberry wine has been underway now for 3 months and the SG is now only 1.030 (it has come down from an OG of 1.090). I'm a very experienced fruit wine maker - hundreds of batches over time - and all my others have gone well, and taste great. This is the second blueberry batch I've made and the other one was really slow too although it finally did finish at .998. Is there something about blueberries I should know about, or do blueberries require special treatment?