The Pet Store recommends only crab pellets but this is false. I feed them something everyday except one day out of the week. I give them crab pellets on most days, live crickets, krill, beetles, worms(they love these) It helps to switch it up. and these crabs will die sometimes, i've come to accept it. It's hard for an animal that has to split out of it's shell to get bigger. Also it's better to treat them like fish and don't handle them too much and don't be too involved with their habitats to stress them out, walk on eggshells persay.
And last but not least, if they don't have plenty of land , they will die. Quickly.