Brown discharge 2 weeks after period, what could it be?

Several things: Mid-cycle is the time of ovulation. Brown discharge between periods could signify one of number of problems, including vaginal infection, endometriosis in uterine or vaginal wall, a spontaneously aborted fertilized egg (yes, one can have a period even though egg fertilization may have occurred, though usually it is not a typical one). See your gp or gynecologist.