What Richard said is on point. So many factors can cause it. Was that plant ever stressed out or anything changed from the others? Closer to the zipper in a grow tent? 10 years ago I had this pheno of DJ Shorts Blueberry that was one of my favorite moms but she would toss nanners if the night/day temperature fluctuated drastically. I learn this trying to force purple plants. Those seeds should be feminized if im not mistaken?