Don’t worry. Your birds are not sick. Birds get hormonal this type of year. When they do that, one bird will sometimes regurgitate for the bird’s person, or they will regurgitate for another bird they like.
Unless you know for sure the bird has other symptoms and also regurgitates, don’t worry about it.
If the bird regurgitates for you, it’s a sign of affection.
If you have a vet, you can call them. They will probably tell you to bring in the bird.