Yes, some plants are able to out compete others for resources. This happens all the time in the wild and is a logical guess for your aquarium given the observations. I've seen similar things in my aquariums as well. When you get a large bunch of a fast growing, or fast absorbing, plant, it's going to take up more resources than a smaller bunch of the same plant will. Personally, I'd like to find something that keeps the glosso growing slowly. 
