That's what i thought i know it can be normal. Were your plants WW's i want to know if a lot of people growing WW get purple stems. my upper leaves are going a bit yellow that's why im getting worried i think it might be related. Look at my grow journal to get a better idea any help would be much appreciated!
All I can tell you is that out of the 10 ww grows I've done, I have never had a purple stem, and my seeds were also from Dutch Passion. Maybe I'm the abnormal one though