First time making a starter, and working with a 2 month old package of WY2308 lager yeast. I boiled 1.5L of starter wort with Pilsner DME and pitched the yeast spread out across 3 mason jars with loose lids and 0.5L each. After 24-36 hours at about 66 degrees and 2-3 agitations/day, I believe that the yeast are active (CO2 definitely comes out of solution when agitated), but there is no krausen formed. IS this slow activity expected, or should I shop for a new batch of liquid yeast?