Shadow effect problem

[nhuminh]

All my two VS-640 and 1 XF-640 have problem with printing light cyan or blue color. All printer using CMYK ink, I think it is cause by Cyan Ink, and I had change another Cyan ink, but all printer still have problem when print light blue color.
And terrible when light blur color with 16 pass. This picture is 8 pass printing.
Any one can help?
Thank you in advance

 

[victor bogdanov]

How does the nozzle test print look

 

[nhuminh]

How does the nozzle test print look

all 3 printer Nozzle test is perfect