my plants look good but seem short,,help

[Hand of Man]

If they are too small, root growth will be seriously restricted and stunt the growth like that.

Gotta agree with Sawleaf (if I understand correctly); I had healthy plants
growing in 2 liter bottles (growing in soil). They got to about 1-1/2 ft tall and stopped
growing. When I transplanted to larger pots the plants took off again!