Dying roaches

So, I've racked my brain to figure out WHY I have nymphs dying and I've not been able to figure it out. They're warm, the have humidity, the have food/water crystals, and there's no mold (clean bins). I understand adults "expiring," but nymphs??? So my wife tells me, "water can mold/ become stagnant." This never occurred to me since I've heard so many people say to put water crystals in a gallon jug of water and fill it up, but where as I have no clue why else they could be dying, I thought... maybe?
But wouldn't that kill them all if that was the problem? It does seem they don't eat much (of their dry chow). The adults go crazy for oranges, apples, bananas, but the don't really go crazy for chow. Even the nymphs don't get all that excited for the fruit either. Or maybe my expectations on how much they should eat is to high. So I made some fresh water crystals and we'll see, but any thoughts would be helpful.

Anybody, anybody???

I would stop using the water crystals. They can get nutrition and hydration from veg scraps and occasional fruit. Just be sure to replace it if it sits for more than a couple of days or starts to get moldy or smelly.