Vet Rx is not a medication. It's an aromatic, like Vicks VapoRub.
If they have actual snotty noses (not just clear, but true snot), they have a bacterial or a viral infection, both of which I would cull them for, as would any breeder. That is my only ever recommendation for contagious respiratory disease.
If it's just sneezing with some minor clear discharge, it could be environmental, either too much ammonia at their level in the coop, or new plywoods/caulks in the coop, or pollen/dust, etc.
Antibiotics will alleviate symptoms of a bacterial infection, but if it's something like Mycoplasmosis/CRD, it leaves them carriers and antibiotics will not fix that.
Viruses do not respond to antibiotics. You would not know what they have unless you have a vet, maybe a state poultry lab, euthanize one and test it for you.