Insufficient light

Too much light is often the reason why some people sabotage their plants' growth. Many journals show photos of the symptoms of a plant under too much light, but very few or none show the symptoms of a plant that is not receiving enough light. What are these? We know that reaching for the light source is often a sign, but this usually occurs in the early stages of growth. But during the growing season? Let's say when the plant is already 50 days old. What symptoms are there that indicate insufficient light?

slow growth and streaching. the plant will be leggy. do you have pix and details of the light being used and your set up and growing medium and feeding regieme. any and all details will help you get a better answer