Ok so heres the problem i have had a blue crayfish for two years now and he has been fine but last week he molted then molted again in the same week and ever since then he has been laying upside down. Its been three days now going on four and he is still alive just not turning right side up. Can someone tell me what is wrong with him.

And he is in a 20 gallon tall tank with 4 fish that dont mess with him and i have a ton of small snails in the tank he likes to eat. And the only thing that has changed since i have got him is that i added 2 new fish right before this happened.