Nematodes are microscopic worm like plant parasites that live in the soil & enter the plant through the roots. Different varieties & each one migrates to a different plant part & does its own special kind of damage, except the root knot nematode, he stays in the roots, & there he does his damage. There's one who migrates up the tomato stem & settles in the nodes, making them swell, looking like arthritis. Then they become brittle & can break. Fungus & bacteria disease both can be carried by nematodes. Its possible you have have root knot nematodes, by what you said about the roots, & its also possible they carried a bacterial disease that affected your buds. Its also possible its one of the nematodes that attack fruit, therefore your buds. Since I can't see your plants up close & personal, its also possible that I'm wrong altogether, but I'd still do the marigold thing to be safe for next season. If you want to use chems, you can probably find something at a hardware/garden store by reading lables. Dia earth might help too. So what percentage got hit? If its a lot, you may be better to harvest early to salvage what you can.~~~PEACE!~~~

Oh the tomato wilts are diseases that effect most members of the nightshade family. Dont think thoes particular wilts cross over to cannabis, or not that I've ever heard of. But anything that devastates the roots severely enough will cause the plants to wilt.