my spur thighed tortoise has a lumpy shell! help!

by angharad rogers
(south wales)

My spur-thighed tortoise is two years old, and even though he has a UVB light in his vivarium, his shell has become very bumpy. I am unsure of whether this is normal or not. I give him calcium powder on his food, and he also eats plenty of green leafy vegetables. I also add vitamins to his dry food. I don't know what to do. Please help!