Worms absolutely love
feed and it's used to fatten them for fishing. I give my worms any mouldy or even questionable feed; it avoids health issues and I don't feel like it's being wasted. They also love
straw bedding and chew through it fine. With your stems and seeds you've basically got weed grain and straw. I like to provide a variety of food options and bedding if I can, but I'm happy with
cardboard. If you use that as a base and add some cardboard and some bits of other stuff it might go faster.
Worms also seem to adapt to their environment if they're hatched in it, so worst case is use adults and their cocoons will hatch out worms better suited.