Using a cheap swamp cooler for my Brandon O Graff. Temp for fermentation was around 68 f last night. I added a frozen gallon of ice before bed, just to make the fermentation happen at the bottom end of ale production temps. Woke up this morning to find out its still bubbling, Krausen gone, and the temp at 62 f. I suspect it dipped below ale temps last night. Is this okay?