There are a few reasons that can cause a dog to cough. Each one may require veterinary treatment to help your dog overcome the cough.
Kennel cough is a very common reason. Sometimes veterinarians prescribe a children's cough suppressant to help with the coughing and sometimes even an antibiotic, but it usually goes away on its own in about 2 weeks. You can try to allow your dogs into a steam filled bathroom at 15 minute intervals to help give them some relief. Considering it is happening in multiple dogs, this is likely, but not definite.
Tracheal collapse is common in smaller breed dogs, but is sometimes can be found in larger breeds, likely not what is going on but I thought I would mention it and you can read more here:
Click here: Tracheal Collapse
Internal parasites can also cause coughing. Roundworm and heartworm are the biggest offenders. Roundworm can be tested with a fecal sample where as heartworm is detected through a blood test. If your babies not on a monthly heartworm treatment, then the risk is very elevated that they could have heartworm. If they have not been tested for heartworm, start there. :)
There are also heart conditions that can cause a dog to cough and wheeze...if you feel this is could be a problem a vet is necessary
They may also have an upper respiratory infection or may even have allergies causing the issue. If its a URI, they will need antibiotics to clear it up if there is eye discharge, this is a pretty good possibility. ;)
It could be allergy related reverse sneezing again, doubtful but worth the mention:
Some dogs can have reactions to Hartz and other types of flea drops, so if she is being treated with such, that could cause coughing. You can read more about canine coughs here:
You can read about the use of Robitussin here:
I am sorry to not be able to pinpoint exactly what is going on, but those are some reasons this could be going on. :) Good luck with them and do let me know how you make out :)