Roots expand before foilage grows - So when a plant is rootbound, the foilage expands to maximum capacity (then slows when it catches up with the roots) Transplnting gives the roots more room to grow, and then the foilage fills in again. Doing it more than once is unnecessary but I would start in a solocup for soil, and then move on to a 5 gallon bucket, that way at least your roots are getting the energy they need.