I had a blue Crayfish a while back and it sheded just after a week of keeping it.
It might've done it just to adjust to its new environment. I would not take out the molt though, Crayfish usually eat their prior molts to gain back precious calcium left in the old carapace. After a week I'd remove whatever's left.
How long ago did it shed by the way? I would quarantine it from the other Crayfish or at least place it in a submerged hamster carrier for the time being. Crayfish are very soft and vulnerable after molting and could be attacked and eaten by the other Crayfish. Separate it from the other Crayfish for a few days while it's new shell hardens.