13 week old kitten skipped two meals..?

I've had her for about a week now. She's been otherwise completely normal, playing a lot and drinking water. I think she may be a bit sleepier than normal, but maybe I'm being paranoid?

Anyways, I didn't change her food. She ate up her first meal well. I gave her her second meal and she ate maybe half of it, but left the rest. I rinsed the bowl and tried giving her dinner, but she isn't interested. I even tried throwing on some crushed up freeze dried minnows.

When is the time to get worried? 🙁