If you only just got your first beetles 4 weeks ago, the baby worms might be too tiny to see. They start off reeeealllly tiny. I have to look really hard right now to spot the worms in my second batch but they are definitely there! I would move the substrate/food from the adult beetles to their own container and wait and see if you see any tiny worms later on. Don't throw it away. I put some in a container once and left it for a long time because I didn't see any worms. I forgot to throw it away and several weeks later checked it before I went to throw it away and I had baby worms! That was a colony I had tried to start a long time ago, but just wait. You should have baby worms soon.