>The clam still has a white rim at the edges so thats a good sign right?<
Yes, good sign. Still I think your light is low unless the clam is right at the top.
>Could it be having trouble footing in the sandbed?<
Crocea's don't live on sand beds. They normally live imbedded in coral rock. If you can find a safe spot for it I'd move it up onto your rock structure (maybe slowly to not shock for change in light).