My dog Is a zu pomeranIan poodle and has a heart murmur but recently he's been coughIng lIke he has a haIrball and coughs up whIte phlemmy stuff and he's never around other dogs

What has the vet said?

What has the vet said?
Um well we don't know we haven't asked I just wanted to see if anyone has any input before we go to vets

Um well we dont know we havent asked I just wanted to see if anyone has any input before we go to vets
How could any of us possibly know? We can't see the dog or feel him or listen to his cough. And no one here is a vet who would even dare to diagnose a dog that he can't see.

Coughing can be a sign of heart disease.
Because your dog has a heart murmur, I would get it checked out at the vet to ensure the disease hasn't progressed.