Yep, when happy they use a huge amount of calcium and alk. It does seem to go in spurts ime but totally white scutes are normal but growth does slow down when larger as they add to the inside of the shell, so the consumption still is huge and increases.I've got an update for you:
The Tridacna's tissues have grown quite a bit.
What's really impressive is the amount of growth of its skeleton. Is it normal?