If your Subpod smells, it indicates that food is rotting before the worms can eat it or there is not enough oxygen in the system.
There are a few types of mite that love a worm composting kit and this is all normal and part of the ecosystem. However, as with most things if they start to take over the kit this can become a problem. There are two main types – a reddish brown mite and a white shiny round mite. Both are tiny and if numbers become huge they eat the food and your worms will tend to burrow deeper into the kit and this in turn stops the worms from reproducing as effectively.