you need much more light! I had plants that looked like that before, and it was because they were sitting on the edge of my light source, in the direction of 2 6500k lights. meaning they weren't getting enough light. nor were they getting enough RED spectrum 2600k
also too much blue spectrum 6500k & Nitrogen, can cause this with certain strains. Usually a high N, doesn't do that much, it just makes the buds airy and more spaced out.
the plant on the right side should look like the left one, dense and heavy, but its all poofy and leafy, it looks FAT haha but its not

plant on the left weighed at 10 grams dry/cured
plant on the right weighed 4 grams dry/cured