Check the top of the chart — "Light".
The shape and structure of the plant in the photo are those of a plant that hasn't received much light. It's short, has a limited number of larger leaves, very few branches, and has grown tall.
The only way that plants can generate energy is when light, water, and carbon dioxide are used to make glucose. As you add more light, a plant will grow more quickly, up to the "light saturation point", and it's almost a direct relationship between increased light and increased yield.
I suspect that's the situation for this plant. It's not that it's unhealthy. The primary issue is that it hasn't received much light.