Transparent tortoise shell

[Tortieporty]

Can anyone explain why my Tortoises shell is like this?
Other tortoises her age (2 years old) seem to have really thick coloured shells with no transparency, she eats a well varied diet (with dust), gets lots of sunlight every week and is bathed regularly, is this normal and will it fill out?

 

[ZEROPILOT]

SURE??? (white squiggly lines)

Hi, Are we sure these are nothing bad? I just had a tort breeder say shell infection? Thanks

tortoiseforum.org

Although no one seems to know why this is only exhibited by some tortoises and not others, it's not a health concern.
I'm sure others can offer a first hand experience. I've never had it in any of my torts