It's not a N def. If it were it would yellow at the bottom leaves and not effect the plant uniformly as it is now. 1. It looks like your slightly overfeeding because of the tip curl. But that's just me. 2. The problem that your having with thr information you provided is a mag problem. I would check your ph to see if its at 6.5. For some reason maybe it's P nutrient or just cannabis in it's flowering state but most growers (myself included) seem to run into ca/mag issues in flower. I wouldn't just throw some calmag at it without first checking your ph and run off that can cause more issues then what your having now. And your right, if it is a 10 week strain I wouldn't expect any yellowing (N def) for another couple of weeks. But your plant looks very pretty. What strain is it?