Help with my crab

[superfish.crab]

so i own 5 fish and a crab a friend got me on my birthday(no one told me what fish they were). And now the crab isnt moving i havent seen him eat and he lost 2 legs yesterday.
(my fish)
2 yellow slightly transpearent fish
2 black long fish
a big fish that cleans the tank
and a crab with orangebody white underbelly and black spots all over
what should i do plz help.