That image shows clear evidence of over-inking of the media (note the areas of shiny black ink). When you lay down more ink than the media can quickly handle/ dry, you are prone to this type of inter-color bleed.
To stop this, you would need to either restrict the amount of ink, and/ or raise the temperatures on the printer to more quickly remove the liquid solvents in the ink. This will allow the ink drops to set and not interact (coalesce) with the adjacent drops of ink.
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