Digital BW, The Print

Hi,
Yesterday I refilled only the Magenta and Cyan cartridges on my 1400 using Eb6 and then also checked inks in all other cartridges one by one.  
Now when I print, the yellow position prints too dark - almost like K ink which sits next to it! Easily seen by printing in Calibration Mode on QTR. What could be going wrong? Anyone had similar experience with 1400? Solution?
ThanksBharat