Yes Boxers have two types of heart condition that are known about
These being Aortic Stenosis (AS) and Cardiomyopathy (BCM/CM).
There is also another that I've heard that two dogs have which is Pulmonic Stenosis.
Certainly it's not one that I am specifically aware of as a problem within the breed.
To read more about these conditions see here
http://www.boxerbreedcouncil.co.ukAlso on this website is the Boxer heart list (you need to click on health and then AS button)
Then there is link to the list from this page, it lists all dogs that have cleared for AS - listed by gender
and the dogs KC registered name in alpha order. So you should be able to see if the parents of your pup were heart tested.
Kennel Cough is still doing the rounds - I know of someone that picked it up from LKA.
It could be that your pup has picked it up again but only a very mild form as it has some antibodies from the last episode.
Best to get your vet to check your pup over to make sure.