I brewed a pale ale yesterday the gravity was low 1.041 but six hours after pitching safale s-04 the airlock had no movement so I pushed down on the lid of the fermentor and then the airlock started moving fast like it was stuck but now everything seemed good. But this morning the airlock is showing no movement it looks like the fermentation is done. I have never seen this happen before but also I have never used that type of yeast before. Should I buy new yeast or just take a new gravity reading? The temp in the fridge is 70F & there should be plenty of oxygen. Suggestions Please!