Did you plant them directly into the bigger pots after they sprouted or did you plant them in smaller containers and transplant? From what I've found out (This is my first go round with auto's) If you plant them directly into larger containers they stay small for a while focusing on root development. If started in smaller containers, The roots fill the space fairly quickly and start to grow a little faster. I had 3 auto's in 3 gallon containers and 3 in plastic cups all started at the same time. The ones started in the cups grew faster. Just my observation.