The stems are so small because the plant is looking for light. Your light is to weak/ to far away from her. Solutions: Go if possible closer to the light. Give soil around the stems, and dig her deeper if you tanplant. Give her airflow ( the lants shoul move alittle from the wind) do some training with her. Take your hand horizontal above the plant, take the "stem" between 2 fingers, and shake the stem. Little cracks apear in the stm and fatten it up. Airlow does the same ( wind in the nature) and getting closer does the same