This is 100% a retcon by Gillen, not Duggan. It was established early on that Krakoa is self-sustaining. The mutants provide enough sustenance to Krakoa for it to grow food, water and shelter for every mutant there. That's kind of the whole point. Krakoa is the perfect place for a mutant nation because they don't have to rely on the outside world. Selling the medicine was just to attain political goals: legitimacy from other countries, immunity for mutants, etc. It's always been the case that the medicines are purely a benefit for Krakoa, not something they rely on.
Then we have this issue, where Gillen says that Krakoa is NOT self-reliant, and instead is absolutely dependent on sales of the drugs, and without them the nation will collapse in a few months. It's a retcon that takes away one of the foundational aspects of Krakoa in order to push momentary peril. I'm surprised Gillen did it, he's usually better than that.