And that's why he was dying in the logan movie... the healing factor was not working anymore...the doctor tried to tell him...
In Logan, the evil doctor explained that they had poisoned the food/water supply to stop mutants from being born. If you stop mutants from being born, you can then sell them to the highest bidders later. But that's why, at least in the movie, Logan was losing his healing powers. The poison specifically destroyed him in a way he couldn't recover from. So even though it was slow and gradual, it hit Logan harder because his healing factor is such a big part of his effectiveness as a warrior.