Since establishing Krakoa as a Mutant Nation, the X-Men seem to be experiencing a poisoning of the mind and soul. It could be through the food that Krakoa provides or just a psionic influence from living there, but somehow, there has been a drastic dark shift for the X-Men since they made the mutant island their home.
The X-Men first encountered Krakoa in Giant-Size X-Men #1 (1975) by Len Wein and Dave Cockrum. Using Charles Xavier's Cerebro, the X-Men detected a very powerful mutant on an island in the South Pacific. When they left to search for it, they found out that the mysterious presence was the island itself and that it was actually a mutant. It attacked the X-Men and tried to use them as sustenance. Right away, the island acted as a predator to the X-Men and saw them as its prey.
Later, Professor X used Cypher and Warlock to experiment on Krakoa to make it a suitable home for all mutants. For most of them, it doesn't seem strange that they are living on an island that was once their enemy. They also didn't have any reservations about using the island as food. In Marauders #1 by Gerry Duggan and Matteo Loli, Iceman tells Kitty that "if you get hungry, everything on this tree is edible and it's really delicious". Since they moved there and consumed the plantlife of Krakoa, something has changed about the X-Men. They have decided to use the names and symbols of some of their worst enemies, which would only have happened if somehow they have been twisted through their use of Krakoa.
In order to distribute medicines made on Krakoa to the world, they have formed the Hellfire Trading Company whose structure mimics the Hellfire Club, one of the X-Men's greatest enemies. Not only did they take the same name, but also retained the club's hierarchy. Instead of having CEOs, the company is run by the White Queen, the Black King, and the Red King, and under them are their bishops and knights. While they had accepted Emma Frost years ago, they still wouldn't want the good that the mutants and their new nation-state bring to the world to be cloaked in the evil deeds of the Hellfire Club.
Kitty Pryde was the only mutant not able to travel to Krakoa through the gates but it seems as though Krakoa has affected her the most. Not only did she change her name to Kate Pryde, which is symbolic because of the dark future it is from, but also decided to call her team The Marauders. Not very long after Kitty joined the X-Men, a team that calling itself The Marauders massacred the Morlocks who were a group of mutants living in the sewers. It was the most brutal mutant massacre and Kitty saw the after-effects herself. When she named her team the Marauders, she claimed that it was because she didn't want it associated with the X-Men. Even so, it's odd that she would choose the name of a group responsible for a terrible massacre, especially one that clearly left a terrible impact on Kitty herself.
These naming conventions on the surface might not look significant individually, but paint a worrying trend when gathered together. The X-Men wouldn't have used these names before they moved onto Krakoa and ate its fruit. The only explanation for these changes in the X-Men would be that Krakoa is somehow influencing them or poisoning their nature.