Fact is, humidity is a major factor in the survival of your Dubia Roach colony. If you have Dubia Roach fatalities for no apparent reason, 9/10 times its due to uncontrolled humidity. How do you control your humidity?
You can easily release large amounts of humidity by cutting a hole on the top lid of your Dubia Roach bin. This will allow moisture to escape the bin so it doesn't build up and cause mold or other fungi's that will kill your Dubia Roaches. Air flow in your bins is key. If you have a hole cut in the top of your bin with screen mesh hot glue over it, keep the piece of plastic you cut out of the lid. You can use this to lay over part of the hole on the bin to limit or let more air in and out of the bin to maintain a healthy humidity level in your Dubia Roach bin.
You want your humidity levels to be around 40% in your Dubia Roach bins. If you live in an area will very low humidity and you find your Roaches are on their backs unable to molt (shed skin) as they should, then this means you do not have enough humidity. This is easily fixed. If you have Water Crystals, then you can add a little heat to the bin to cause humidity to rise (put these in a dish of some sort that the Dubia Roaches can climb - this prevents waters from puddling and drowning them). Also Dubia Roaches sweat like human beings do so you will notice if you have heat pads or other methods for heating your bin you will notice your Dubia Roaches will sweat more and raise the humidity levels.
If you live in an area with too much humidity and you’re having trouble getting it lower than 60% do not resort to wood pellets or other ways of absorbing moisture... This contaminates the bin and when the Dubia Roaches eats parts of it you will notice them dying daily. Cut larger holes in your bin with screen mesh hot glued on it. You may even consider putting 2 holes on opposite sides of the bin (small ends) to allow air flow to pass through the bin. You could also set a small desk fan on low to blow through the entire bin to dry it up a bit in there. You will find the fan cannot be too close as even on low the fan is extreme for the small bin size most Dubia Roach owners have and they will have trouble with temperature etc.
There is a lot to consider with housing Dubia Roaches but as you experiment with them you will find the best solution to keeping them. Don't get discouraged. Most first time owners run into issues like this and they lose whole Dubia Roach colonies. They can be very temperamental but once you and your Dubia Roaches get on the same page you will see your colony thrive.