According to the MSDA for Ifotec DDX, it is a Phenidone/Hydroquinone formulation. This means that it is susceptible to Phenidone oxidation (no color change with this!) and a consequent sudden and dramatic loss of developer activity.
A Google search reveals that Ifotec DDX is described as "a lovely developer with a limited shelf life."
Try a test piece of the film in a different developer.