Welcome to R2R! Aside from possible molting, or just stressed out from a new move, if you live in a part of the world where it is currently winter, your crab may not be getting enough humidity (prefers at least 75%) or heat (prefers temps 75-85F). They also need access to both fresh water (not tap) and saltwater. As you know, the habitat should be sized up as soon as you can do it, with some sand or moss added.