Red stems

Hey Growmie, Unfortunately, this could be from an array of things like strong direct light, Genetics, Temperature Fluctuations (temp too cold at night), Plant Stress, Nutrient Deficiency Caused by Lack of Nutrients, Nutrient Deficiency Caused by the Wrong PH, but judging from how happy you plant looks in the picture I would put my money on it being the from the direct light, and as long as the plant keeps looking this good you have nothing to worry about. Feel free to shoot me a holler if you ever need any help, I'd be honored to assist you. Hopefully, this was helpful, and remember ... "Happy Growing" and "Free your mind one puff at a time".