Are the young dying off or are they being eaten by the adults. In other words are you finding their dead bodies or are they just disappearing on you? That might well be the key to what is going on as they could be very different colony dynamics or illness or a husbandry issue.

Since you use glass tanks my question would be temps. Are they in any direct contact with sunlight shining in? What's the room temps like where they are kept? Do they have constant access to water and food? Is the water bottle spigot low enough that even the smallest young can easily reach it?