Please let me know how your revisions are going. Although not a biologist, I tried to think of ways to explain the "10" plants not growing as fast as the others. Maybe the point of the experiment was to find the anomaly. Years ago, I had a geology professor who taught us by using what he called “traps.â€ In these traps, we would all find the same obvious answer, but that was only the starting point for the “realâ€ answer. Perhaps your professor set a trap. Good luck.