What Causes Brown Vaginal Discharge While On Azithromycin?

Hi, I recently had a respiratory respiration. My doctor prescribed azithromycin for five day. I finished all my pills, but I am still using this nasal spray and an inhaler to clear up my lungs. Now, I am getting brown discharge. Is the brown discharge related to all the medication I am on? Also, the last time I had my period was 2 weeks ago