66-68F should be plenty warm if you get yeast back in suspension . what was your mash schedule and OG and starter size. this yeast should have done fine in the mid to high 50's-similar to kolsch 029.
I started the partial mash at 152F for an hour although temp was at 144F at the end. OG was 1.052. Yeast starter was the White Labs instructions of 2 pints water and 1/2 cup DME.
so that's a small starter. you had about 940ml starter at 1.042OG producing about 230BB cells. and even with fairly fresh yeast that's not enough -especially for cooler fermentation. i would target 275BB-300BB , so around 1800-2000ml at 1.030OG.
also the mash lost a lot of heat over an hour. using a cooler? may want to upgrade to thicker wall cooler if your losing that much heat.
edit: what was date on your yeast? generally, 1000ml is smallest recommended amount of wort for starter. smallest i use is 1400ml and i target lower OG of 1.030-1.032. using a stir plate or shaking? i use http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/
to determine my starters as well as prior experience with the recipe and yeast. like i mentioned, i shoot for more yeast cells for cooler fermented ales.