Tips for extremely picky eater?

I recently adopted a pitbull, and she’s been extremely picky with her food. She wouldn’t eat the kibble they gave me from the shelter, which they said she was eating there. After about four days of only nibbling on it, she started looking unwell. I called the shelter and found out they were mixing it with wet food, which worked for a few days, but now she’s refusing to eat it again. She’s been eating grass and seems low on energy, so I’m worried she might be sick.

The shelter also suggested feeding her pumpkin puree if her stomach seemed upset, but she only ate one spoonful. I’ll take her to the vet if this keeps up, but I’m curious—what kinds of food have helped you get your dogs to eat their kibble? I’ve read that adding chicken or beef broth can sometimes help.