I think with the 3 plants, you can fill the tent quite well. Another 5 to 6 weeks of veg and then into flowering. But I would base it on a few factors. How well is the climate balanced, ventilation of the canopy, and how much do you want to harvest? With the 3 plants, it will probably run more stress-free, but after the rather short veg, you might get a bit less out. Good luck!