What can I do for my bird when I dont know what's wrong?

I have two parrots. A boy (Romeo) and a girl (Juliet). Juliet has been acting really weird. It’s hard for her to walk now. She can’t climb the railing at all now. She can’t fly. Nothing. I don’t know what’s wrong with her! And I’m really worried and upset. I got a low food dish for her to eat out of because she couldn’t even perch up on the other one. But her beak was too long. So I got one of those filers for the birds. She filed it down. And has been eating. I thought maybe that was it, that she couldn’t eat. But it’s been a couple weeks. And she’s just getting worse. My family thinks maybe she had a stroke or something. Can that happen? Or a heart attack? She isn’t that old. And at first I thought maybe Romeo had hurt her or something in a fight. But no feathers were found. And he’s usually next to her all the time! Cleaning her. So I don’t think he did anything. Has this happened to anyone else’s birds? Can it be a disease? What can I do? I don’t have enough money to take her to the vet.