Epson 4900 after cleaning cycles the nozzle test is terrible

Hi all, last time when i have this problem, i cleaned the whole ink supply system with distilled water ( ink hoses, dampers,carts , but i didn’t touch the head) and after this everything works perfect but after few days the problems come back, so the problem is i do a nozzle check and my black channel was doing stupid things, after cleaning cycles, slowly slowly the whole channel was disappear from test pattern print, so i replaced the damper assembly ( the whole unit ) now my black is working 100% but the cyan doing the same thing, i replaced the capping station unit aswell 1 month ago. what can be cause this problem? i know the head is working 100% its not clogged, the capping station is new, the damper unit is new, so now what can be the problem? the refill carts?