A healthy cuttlefish that feels secure in its surroundings is very likely to 'beg' for food and train its owner to give it more than it needs - especially if it is being fed live food. Excess, uneaten food should be removed, as it will rot and may cause an ammonia spike. Proportions should also be reduced past the point where the little beast is able to eat everything. If your cuttlefish isn't eating very much of the frozen food that you are offering, switch back to live food for a while. Underfeeding can also be a problem.
Cephalopods can be cannibalistic especially when they are underfed.
Cuttlefish generally eat the meat out from crustaceans and discard the shells, but they ingest entire fish. Cuttlefish have a large cuttlebone, and they may get some of the calcium for it from their diet. It might be a good idea to occasionally fed them whole fish, either live or frozen. Now you not only know where to purchase a cuttlefish, but what to feed one, how to filter the tank and what tank mates are likely to remain alive. There is only one question left.