I don't think vet RX is going to do anything for draft-caused pneumonia, especially since "pneumonia" isn't a disease. If an animal has pneumonia, that animal has fluid in its lungs. It can be caused by a viral, bacterial, or fungal infection, an anatomical defect, by aspiration, by inhalation of a harmful substance, and I'm sure some others.
If there's a draft, the solution is not anything you put in the water. The solution is to stop the draft.
If there's a draft and they're trampling each other, they're probably too cold and need more protection from the draft. You need to fix the environment they're in.
Welcome. I hope you find the information you need.