Very unlikely that the aerosol fan is directly related to this.
The L25500 prints Y/K ink from two printheads as I recall. What are you seeing when you run the Printhead Test Print (on the printer's control panel: Ink Menu > Image Quality Maintenance > Clean Printheads > Test Print)? If you are seeing cross contamination between the two channels (black in the yellow channel or vice versa), run one or more cleanings (for those heads only) to attempt to clear it up. It may take a couple of cleaning cycles, but it can generally be resolved in this manner. The worst-case scenario is replacement of the head (a consumable), which takes about 10 minutes to complete, including the alignment calibration routine.
Paul