The short answer is yes it's normal and no it's not. Purple or red stems where the red or purple running down into the leaf veins coupled with yellowing, and a host of other symptoms such as browning and dried out spots would be indicative of deficiencies. Your plant looks healthy and that purpling looks normal to me but. Missing information that is helpful to others. What are you growing in? Feeding what? You should know what your pH is it would help us too. Remind me again what strain she is.? I will put up a pic of a very healthy lady with lots of purple and reddening if you are interested in seeing it. Good luck