What Causes Bad Odor Brownish Vaginal Discharge?

I am a 45 year old women,healthy and active. My last period was fine until a few days later I had a foul smelling dark brown discharge for about 2-3 days - honestly I've never smelt anything like it. I have just started this month's period and it smells ansolutely fowl but is very bright red almost orange. Can you please help.