He could have any one of a number of poultry respiratory diseases, there is no way to know exactly what he has without having some tests done. Sometimes a hoarse voice that turns into a wet cough can be a sign of infectious bronchitis. But many of these diseases mimic each other as far as symptoms. Some are viral some are bacterial, the problem with all of them is that they very easily turn right into pneumonia and secondary bacterial infections. For that reason antibiotic's are usually given if one does not plan to cull the sick bird. Most of these diseases are not considered curable, even with antibiotic's, because the birds remain carriers of the disease in most cases, with the potential to continue spreading the disease to other birds.
VetRx is similar to menthol products humans use when they have a cold. It may help thin mucous secretions and make it easier to breath if a bird is very congested. It won't cure anything however. The bird will either recover on it's own or it won't. Most pet stores that sell bird products will carry VetRx.
