A little too calm

My past 5 batches or so, I've noticed a real lack of krausen during fermentation. A real lack meaning only a 1/4" ring or so and many of the beers seem to be stopping at a FG higher than I feel they should be. I do BIAB 5 gallon batches and ferment in a chest freezer with a temp control that keeps things at about 64*F ambient. The batches in question have used dry yeast and liquid yeast (no starters, but mostly pitched 2 vials to compensate). Only one of these batches has turned out to my liking. Any thoughts on what may be happening to my krausen-challenged beers?

Two thoughts:
First, Unless you are pitching a lot of yeast, which you're not, try raising your fermentation temp to 69.
Second, Perhaps you're mashing at too high temp. Calibrate your thermometer (just in case) and aim for 152 so that you can being out more fermentable sugars and see if it makes a difference.