Hmmmm...i've never really put it on paper quite so rigidly as to chart it. I go more by root development than height/width anyway.
What types of strains are you running? What type of pot? Planting medium? These are all relative to whether or not you are in the right size pot.
Most of the indica dominant strains i work with - once roots show through cube - are transplanted to 16 oz cups for about a week or until they start showing signs of vigorous veg growth and roots are well developed in the cup under T5's @ 24/0 . Then they go to 1 gallon pots for another couple weeks or, again, until roots are well developed under 1000 watt MH @ 18/6. Next step is 3 gallon smart pots when roots are ready through flower under 2000 watts of dual arc HPS/MH @ 12/12. Avg canopy height in my garden is roughly 3' after stretch in flower with this technique.
If i were you, i'd gently pull a root ball from a pot and see if it looks root bound. If so, transplant. If not, you've got another issue. Temp, infections, root damage, etc can all lead to slowed growth.
Hope that helps. Best of luck with the grow!