Hi, I bath my Indian star tortoise in warm water daily (she is 4 years old.) when I bathed her tonight she passed a huge stone about 1cm by 2 cm which caused her some distress. It was grey in colour and hard like a stone. Does any one know what this is and how I can prevent it happening again. She is kept in a tortoise table on newspaper and hay in the bedding area. Shaw eats mainly salad leaves with carrot