Coughing Guinea pig is huffing and coughing?

Hey guys, well anyways I am on vacation visiting in-laws and took my guinea pigs with me. First off my guinea pigs has never coughed back at home just a little huff noise when laying down. One of my guinea pigs coughed twice today once when putting him back in the cage and another while he was eating his fecal matter. They are both huffing when they exhale at times too. I don't think their sick they seem to be eating/drinking normally and gaining weight properly. My in-laws however they live in a pretty humid place, Charleston, SC. My in-laws houses are kept nicely and look nice but the house itself is old, dusty, and has a moldy smell. Do you think the strange new smells are agitating my guinea pigs lungs? They just started coughing when we got to my hubby's grandma's house. They have no nose discharges or crusty eyes, no loss of appetite, no crust/flake on nose, and no weight loss so I want to rule out URI but if any of these other symptoms occur in the next 2 weeks I'm taking them to a vet visit as soon as possible.