Auzures died at certain stage

[Tropicok]

A friend gave me six azureus eggs to hatch for him. The tadpoles were doing fine, eating & growing but when they got to the stage where the tail disappears and the limbs are grown they die. What is causing this?

[nos187]

Could you give more details to your procedure?
Once the legs are grown they need and escape from the water or they will drown.
A step by step list of your procedure may help come to a conclusion.