Advice with cough (with video)

I took my dog a couple weeks ago to the vet for a nasty cough, puking, and shaking- he got X-rays to make sure nothing was stuck in his throat and was diagnosed with pneumonia and mild fluid around lungs. He went on antibiotics for 10 days and symptoms completely went away. A few days ago the cough started back. Only happens at night. I finally got it on camera and it’s a pretty distinct cough so I was wondering if anyone has any advice on what it might be. I have been researching collapsed trachea and allergies but neither seems to completely line up. Any advice is appreciated!