Yellow Contamination Noz Check

That yellow nozzle check does not look healthy.
Check that the pump is pulling through properly as the small outlet pipes below the cap can block especially at the small double connector.
Possibly the cap top is touching the printhead which causes wicking and cross contaminates the prints.
Personally I try to change the complete cleaning station once a year as they wear and just changing caps, wipers and other parts doesn't help sometimes.

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Looking further all your nozzles do not look that well (of the ones I can see).
The biggest issue and major factor I see on these printers is lack of use.
If not used they tend to block up and you loose nozzles a lot more easily.

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When was the last time you replaced your maintenance station. If it's been more than a year, that's the place to start. As Heyskull said, the pump could be going and/or the cap top could be swollen and causing ink to wick across channels.
Even if you soak your head, without a competent maintenance station, you won't be able to clean the head effectively and even if you could, you're likely to cross contaminate the head again.
One more thought, have you manually checked the ink levels in your yellow cartridge? If it's low and the black is nearly full, this pressure difference can cause the ink to migrate over - but the cap top would be playing a part here as well. Having balanced cartridge levels may alleviate the problem long enough for you to get a job or two out though.

Good Luck