James, So sorry to hear about your loss. Whereas, it is a part of nature it can be upsetting. It's difficult to say why the other eggs didn't hatch as there are so many variables.
Same thing goes for the deformed duckling.
Yes, it is possible for a duckling to die that has gotten too wet. This is where the extra humidity comes from. If there is only 1 duckling left you might suggest acquiring it a companion so it won't be too lonely. You might suggest that your teacher read these posts or email us, as we'd be glad to explain anything to them. Hope this helps.