Make sure you wash your vegetables thoroughly before giving them to your grasshopper to remove any residual pesticides.
To keep this from happening, make sure your grasshopper has plenty of room to roam and grow in whatever container you have them in. And don’t put too many grasshoppers together in the same container. As long as they have enough space and don’t feel too close to other grasshoppers, your grasshopper won’t turn into a locust.
Note: the sand should be moist, not wet or muddy.