Multiple problems, mainly your roots. Probably not enough drainage and over-watering. Your roots are not able to breath and are under-developed. Now they can’t use all the nutritions the plant needs.
Get some good substrate, maybe even invest in bio bizz. At least perlite for your substrate. And re-pot asap. Its not too late, she will be back if you give her the chance.
If you have a bigger pot, use it! Cannabis needs a lot of space for the roots. They are “Tiefenwurzeler”, not sure how to translate that one ;)