What Could Cause Irregularity In Periods?

My 9 1/2 yr. old daughter started her period last week. She is not overweight at all. It was preceded for a few days by some discharge. Then it started "normally" and lasted a week. The last couple days were a dark brown discharge. Then she appeared to be "done", however suddenly tonight she began bleeding vaginally, a bright red. Should I expect her to be "irregular" due to her age and the fact this is her first period, or is this something to be concerned about? Should I take her to an OB/GYN?