I brewed a porter and i believe i did everything right. Got an og of 1.071 which was just a bit high. Did a yeast starter, shook the wort before and and after i pitched the yeast. Used a blow off tube and fermentation started all out that night. It was bubbleing out the 1 inch blow off tube like it would through an airlock. Problem is after one day it slowed to a crawl and then it seemed to stop almost completely. I checked the fg after a week and was dissappointed to get a reading of 1.035. Was hoping for something around 1.020. Is there anything i can do to jumpstart the fermentation.