Help! Brown Hair I don't know what to do?

I am an African American male with black hair that looks brown in the light. i have an afrohawk (Mohawk that stands up like an Afro about 3 inches tall) and i was smoothing my hair forward with plain water (low-maintenance hairstyle) and i found a single light brown hair just now. I mean it was very very light.It really scares me. Is something happening? I'm not very stressed so it can't be that. Yesterday i used Nizoral dandruff shampoo (two washes) cuz i have an itchy scalp and Palmers Olive Oil conditioner. Hope all of this information helps. Please help I'm really worried.