Could The Spotting After 2 Weeks Of Menstruation Be Due To Atkins Diet?

I had a normal period two weeks ago, last night I started spotting, the color was very light pink and then brown, now the spotting seems a littler heavier. I've been on birth control for years and my periods have always been like clock work. this is very unusual for me. I started the Atkins diet 4 weeks ago, I'm not sure maybe this change is because of my diet, but I've done the diet before with no effects like this. Why do you think?