The gigas in the first set of pictures, appears bleached out to me.
A couple months of proper calcium levels and some TLC, she'll be loooking good.
When I got my larger gigas, it looked like yours if not worse, Now look at my picture.
I have a smaller ORA gigas next to it.
EDIT: Here's a video clip of my clown in my gigas...
YouTube - False Percula clownfish hosting T. Gigas clam