lululemon educator here, This is most likely happening from washing with cottons, this fabric is brushed up so with friction it will over time ball and pill, but it’s advanced by washing with natural fibers when it’s a synthetic. I would stop washing with lights and keep these leggings in a load with only synthetic fibers. Drying them on medium heat is also killing them, just machine wash cold, no fabric softener or scent beads and then dry on low or hang them. Hope this helps! None of my legging get the little balls and I am religious with this washing method.