I made the mistake of planting several week old babies in large ( 3 gal.) pots. I then watched as they didn't get any larger for weeks! I have since discovered , that what would happen, is the plant was putting down roots to fill the pots. So after 3 weeks or so they then started growing again. I too was worried that I had either damaged the plants somehow, or the I was doing something else wrong. They are all doing great now at week 4 of flower. 36 plus inches and covered with flowers and the triks starting frost.

Mine were short, indic predominant strains, I transfered them to flower when they where 16 to 18 inches ( at about 6 weeks into veg) and used a good organic fert/nute system.

Don't dispare, the plants look healthy, if you have a good soil, then around week 4 or 5 you can start giving them 1/4 to 1/2 streangth nutes and see how they react to it.
( I use botanicare organic )