I'm so glad that more people are keeping these awesome little Tenebrionids! A large group of them can be easily sustained once a minimal set of needs are met, and I love observing their goofy behaviors, especially the male dominance struggles.
My group stabilized and started thriving when I got the humidity/moisture right. They don't need to be kept constantly damp, but I did have all my adults die at once when I allowed them to dry out too much. Mold will grow on the fungus if it stays too wet, so good ventilation has been important for mine. They have a couple of thick brown bracket mushrooms as their main food/home/nursery, but they go nuts for the occasional treat of small white soft fresh brackets (and will even lay eggs on them!). I can't imagine these thin white brackets being sufficient to rear larvae inside (not enough room or protection), and they're eaten away fast by adults. But the adults swarm them until they're gone when I put them in.