it's the combination of temperature and light levels, at lower light they don't grow upwards as fast at lower temps but at higher temps they also grow up faster
high light levels and hot they stretch more than if they were kept cool at the same time
if they were grown in a greenhouse then it wasn't ventilated enough probably
Disagree a bit here, low light causes the plant cells to swell and elongate. This is the process that causes the leaves on stems to turn toward the light, the lit side cells are shorter than the shaded side cells. When the stalk elongates evenly, it means both stem cell sides are elongating to push the leaves further toward the light source.
