Hi again, and you're most welcome. Thanks very much for your reply and your accept.
I didn't recommend putting him in the steamed up bathroom, just in case he may have any unknown heart conditions, like cardiomyopathy; I don't want to alarm you, just to inform. Coughing may be an initial symptom, but since you said he's NOT coughing, and neither are any of your other dogs, it's most likely not heart-related.
If he's not coughing and your other dogs are also beginning to exhibit these same symptoms, it's most likely a URI that's going through your canine household, brought in by your female, after her spay. It's not uncommon for a dog to bring home and share her germs, after time at the vet's office.
Do your best with the humidifier and bring him to the vet tom'w, as you mentioned, and if you want to bring them all into the steamed up bathroom, it should be alright. I hope all your furry buddies will be fine!
Cher (sending this as a 'request for information', just so you're not prompted to click 'accept' an additional time)