Rip Beer. You say store bought filtered...but do you mean distilled? I'm not sure exactly what's in the burton salts b/c I haven't used them, but if your using distilled and brewing all-grain, you need the proper levels of calcium and magnesium for yeast health. 64-68 isn't too bad, but even a sudden 4 or 5 degree drop in temp can slow yeast activity.
Originally Posted by Shwagger
The temp fluctuates at night, but isnt colder than 60 or warmer than 70. Its pretty stable. During the summer months with the AC on, the temp didnt flux at all, and the same problems arise. But its always with liquid yeasts.
Schag- a 10 degree temp swing is pretty big. Going from 70 to 60 would definately put your yeast to sleep. Try wrapping your fermenter in blankets overnight if the temp swing is that severe. I would suspect that that is your problem.
I've made plenty of beers with liquid yeast and no starter, (even though its always better to do one) with no attenuation problems. but I always keep the temp steady. If I had 5-10 degree swings in my ferment temp, I would take care of that before you worry about building bigger starters. A 1 Liter starter with intermittent shaking should double your cell count I think.