Humidity and poor nutrition sounds like half of it. You need to mist with water, and instead of aspen which might be harmful try lining with paper towels or coco fiber or repti bark wood chips.
They need apples, bananas, romaine lettuce, oranges, moist white bread and cat kibble, mango, watermelon, and oak leaves to eat.
Was that one your holding attacked? Do you have any alive that deformed? I've raised some pretty damaged hissers and all survived and healed I find it fun helping them! What species is this?