UPDATE 8/18/23: Took Gunner to the vet today, vet caught a heart murmur, did a scan (2 views) and has enlarged heart. I didn't get much info on a detailed diagnosis but I think it's a B2 MMVD. He's on 2.5mg BID Vetmedin (pimobendan) and 1 tablet of antibiotic doxycycline for the likely/suspected...