After reviewing your order history, I see the last time you bought Piezography (Warm-Neutral) ink was in Sept 2013. What are the lot#s and expiration dates on your ink bottles? Based on your last order date, I assume they are expired, or due to expire soon (pigment inks have about a 2 yr shelf life).
Along with printing an Ink Separation sheet every week, cartridges should be regularly agitated (every week or two) to maintain in-suspension ink in both carts and the printer’s internal ink system.
I recommend emptying your cyan/shade 2 cart and refilling with fresh/new ink, though if all inks are old, it would best to refill all carts with fresh ink for the best/consistent results.