If it looks healthy but is growing slowly, you could try to increase your temperature. The growth rate (yield) will depend on the environment and the strain, as 420burn has said, and can really only be decreased from some unknown maximum by deviations from ideal conditions. Personally, I only increase nutrients if the plant looks deficient. I never try to make a plant grow faster or slower, just to maintain ideal temperature, water, and nutrient conditions such that the plants aren't turning colors prematurely or showing nutrient burn.