I personally have noted a HUGE difference in kraeusen thickness between batches (even identical recipe batches) that I fermented at 65 and at 68. Those few degrees seem to make a huge difference in yeast activity.
Specifically, I'm thinking about two batches of my IPA. The 65F batch had only about 1/2 to 3/4 inch of kraeusen. The 68F batch had about 4 inches and made we worried that I was going to have my first ever blow-out. Recipe was 99% identical.
Ground Fault Brewing Co.