First, I'd switch over to bran instead of oats; you can pour it over the top of everything as needed. They just perform so much better on bran and you'll have fewer problems. Having a lid on the colony is also problematic. It reduces the amount of air exchanged and creates unfavorable conditions for the colony. I wouldn't cover it with anything that restricts airflow more than a window screen would. It's not at all unusual to see a number of larvae die before pupating after they've been shipped, so the dead ones might not mean all that much in terms of the conditions in your colony right now. Lately I'd been keeping my colony in a metal shed outside, but on the hottest days it gets too hot inside so I bring it into the garage. They're just fine with an ambient temperature up to about 115, but higher temps start to cause more problems. Finally, feed vegetable material regularly. The more consistent their access is to fresh vegetables, the better your colony will perform. Frequent feedings of very thinly sliced potatoes (1/8") are better than thicker chunks fed less often.
