They were leggy because of the lack of proper sunlight. I doubt very much that there will be any new growth emerging from those green stems.

As a general rule if you cut something back always cut to just above a leaf node. Some plants will sprout from the stem but many won't so stay on the safe side.

I agree that they had too little light. No amount of cutting back will make etiolated plants bush out unless they also have enough light.

To add to what others have said, trimming off only 1/3 of the living plant material (esp. the leaves) is the general rule of thumb to harvesting plant material or pruning if you intend for the plant to recover and continue to grow.

I would suggest starting new seeds with increased lighting.

FataMorgana