Does Brett act differently to sacc in a starter?

So I'm using Brett for only the second time, I got a pack of omega labs 'all the bretts' for a pale ale I'm making...

The yeast pack had no packaging date on it, which I find odd.

I'm making a starter so I can pitch some for secondary ferment of the pale ale and keep some for the future.

Pitched 24 hours ago into a 1.5l starter, on a stir plate, and there is no sign of activity at all. I'm used to there being bubbles and krausen forming by now with every sacc yeast I've ever used...

Am I worrying about nothing? Or could the yeast all be dead?

I'd post a picture but it's literally just a completely unremarkable flask on a stir plate. Although it's a Lego stir plate, so that's something I suppose...

Thanks guys!