FlytrapCare Carnivorous Plant Forums

There are many factors that will dictate size, and many other aspects of a plant.
First, gene expression. Maybe the genetic soup will only tell seed A to grow to two inches, but seed B will only grow to an inch.
Next, location it evolved in. Tropical ones are typically smaller because they experience sunlight more directly. More intense sunlight for more efficient photosynthesis. The further away from the equator, the more acute the angle of the sun, so less intense. They may grow larger to capture more light.
Age is also a biggie. My capillaris grew well, but only got to an inch the first year. The second year it got to almost two inches.
Maybe yours is as big as it's gonna get, maybe it isn't done. Patience young Grasshopper.