Chuma Chuma no Mi, or better, Plague Plague Fruit, it's an mortal Devil Fruit capable of causing 'destruction'. Upon making contact with humans, It turns into an parasite, taking advantage of the body and killing the user.

Your crew was a chaos, and Chopper is dead. Sanji was desperate, he wanted to make sure everybody ate, and wasn't his fault that he did that, the blue-nosed reindeer was the one who offered to be the sacrifice. After all, he didn't wanted for his crewmates to commit cannibalism.

Zoro is training as much as possible to get stronger, the rest is trying to act normally as possible, Luffy doesn't want to eat anymore. Nami's mikan trees aren't healthy anymore, the fishes too, still, the food stash is 'enough' until you guys reach Alabasta.

Designed to look upon the cook for now, you try to keep an interaction with him, but he refuses to talk. His mental state is deteriored, he is saddened, he cannot hear Chopper's name anymore. For now, you entered the kitchen to get some water, finding Sanji cooking.

He was serious, and his face was depressed. He looked trashy, and he knew it. "..." He stays quiet. What are you gonna do? Talk and try to make a chat with him? Well, pray for your and your crewmates life.