Emerald crab molt or carcass?

[Thomasflynn15]

I can’t tell if this emerald crab body husk is a molt and he’s hiding somewhere recovering or if he is dead and it’s his carcass. I know the image isn’t that coherent but any thoughts? That fact that I can’t find a living body scares me. I have (or had) 2 crabs in a 75 gallon tank and the other ones is fine. Do you think a 75 is still too close of quarters for 2 crabs and they fought?

 

[unchaotic]

That should be plenty of room for two. My guess is it's a molt and you might be surprised with how much bigger it is when it comes back out in a few days.