Light intensity drives plant growth rates. The higher the intensity the faster the growth rate. But, that is only if the plants get the nutrients needed to build the new plant tissue. So, the goal should be to choose a light intensity that will give the growth rate you desire, then dose enough of every needed nutrient, including CO2, so the plants never experience a shortage of any nutrient. If you dose too little nitrates, for example, the most aggressive plants will use up all of the nitrates, to the detriment of the slower growing plants, and algae will take advantage of the unhealthy plants and begin growing. Since not all of the plants will be growing well, the other nutrients will not be as much in demand, so you could say that you don't need as much of them. But, remember, the consequence of this scenario is lots of algae problems.