Slow yeast starter activity questions.

I've had a couple starters not get going very well recently and wanted to see if there is anything I'm not considering. They've both been with washed WLP011 European Ale Yeast. I love this yeast for it's malty characteristic. In order to simplify my yeast starter making nights I began pre-making the starter wort and putting it in mason jars. Then when I need to make a starter all I do is pull a jar or two of starter wort and a jar of my washed yeast out of the fridge the morning of the night i'm going to make the starter. Since I usually brew in the evenings I'll make my starter 24 hours before I'm planning on pitching yeast for my brew. BTW, I use a stir plate for my starters. This has worked great many times but a couple times the starter hadn't taken off by the time I was ready to pitch, again approx. 24 hours after making the starter. Both times I bailed on the starter and just pitched a dry yeast as a backup. However, last night I decided to leave the starter on the stir plate to see if the yeast would ever take off. This morning, now 36 hours after initially making my starter, I'm finally seeing a krausen form in my starter. This one also was the first starter that I used my new oxygenation setup in. I gave it about 15 seconds of oxygen initially. Once I didn't notice a krausen after about 18 hours I gave it another 10 second burst of oxygen too. It was a 1L starter. The washed yeast was 2 months in the fridge.

So could be going on here? Is my washed yeast not surviving the fridge time. It's a bummer when you go through the hassle of making a starter and then not get to use it when it's game-time.

Thanks

Yeast dont like the cold and they wont wake up very quickly when you've brought their temp down like that. The longer they stay cold, the longer they take to respond to a new environment. I'd tender a guess here that they're just being sluggish and you have to give them longer.

Try pitching a small amount into about 20ml of 1020 wort and see if they respond better at that age. You'll know if your yeast is lagging by doing a small test on it.

i have a question for you guys. is it possible to use something else that dry malt extract for yeast starter?