Normally dogs do not get hairballs. Mostly cats, rabbits, and castles get it. What I am suspecting from it is your puppies are suffering from heartworms. There can be another reason that your puppies are showing these symptoms. It can be kennel cough or just its initial stage. It is a fatal disease, so don't ignore it, and get your pet visit its vet. Otherwise you will find it difficult to control. It can be reversing sneezing as well. But what I get out of it is, there are more chances of heartworm than anything else. Just take it to vet for a thorough examination.
My puppy is not active and wants to just sleep. Normally he is very active. Why is he acting like this.