Yup, more light. Below is a thread to help with the stretching issue. If you try and train them to a stake, they tend to need the stake till harvest. I carefully bury the stem almost up to the cotelydons (baby leaves) on every sativa dominate I grow. Some of my indica doms benefit from this too. Tiz a tad late to control the stretch, but I'd keep a circulating fan on 'em, too. (strengthens the stems)

Stretching seedling fix...