My one-month-old puppy was just brought home yesterday; it smelled a bit so I bathed and dried it, but now it seems unwell.

A one-month-old puppy being listless after a bath is probably chilled, and because it just entered a new home it may be stressed, with weaker immunity, so bacteria can invade more easily during bathing. Keep the puppy warm to avoid further chilling and colds, and give it some pet probiotics to support gut health and prevent bacteria-related gastrointestinal inflammation.

Finally, watch it closely: if it stays lethargic and loses appetite, or shows vomiting, diarrhea, fever, sneezing, or coughing, take it to a vet promptly to rule out infectious diseases such as canine distemper or parvovirus.