My 5 week old lovebird won't eat baby formula anymore. She was eating it for the past 2 weeks with no issues but now she'll just vomit it out and won't eat more than 2 drops. She'll only eat bananas and apples (haven't tried anything else). Can someone please explain what's going on? I took her to the vet and they gave me antibiotics but she doesn't look sick. She's very active and jumps around in her cage. Please help!