Maybe because Willow got some tuna, Tigger did not want to be left out.
I wouldn’t worry about this one time thing, but if you start noticing other behavioral changes, or other changes regardless of what they are, to check with a vet.
My cat started drinking a lot of water, and it’s usually related to kidney disease, but he was checked and there’s nothing wrong with him. I was worried too, that he was sick. But he isn’t.
They can’t talk to us so when we see a change in what they normally do, we get worried.