What Causes Delayed Periods While On Non Hormone Coil?

hi there, i am on the non hormone coil i have my period on the 12th of every month last month was a bit diff after i had my 7 days a week and a week and a half later i started spotting and it was brown discharge and that lasted 5/7 days and now my period is late all up to date with health checks and never had this problem b4 , what do u think could be the problem ?