About every 4 weeks, we try to give the onions and leeks a trim, cutting them back to about 4”.  The theory is that this encourages them to develop thicker, stouter stems.  That may be, but for us, it’s really more about making them fit under the lights!  At 6 weeks, we waited longer than we should have for these plants.  They’ve been brushing the lights for a week now.  But after their haircut, they look (and fit) much better.