JRT smitten

I have a nine month old fe JRT and have always felt she had a weakness in her throat.Had it checked several months ago by the vet and he said he thought her throat was normal so put her on a harness from the very first.In the past couple of days she has a gaging caugh,but not with any regularity nor was she doing any particular thing to cause the caugh.She has been vacinated for kennal caugh but does go to the dog park. I recently met another JRT owner and her dog caughs also . Is this a JRT problem and if so What??????