Q:
A: Are you speaking of a blank spot on the page? If that is the case it actually isn't your toner, it is your drum unit. Check in you supply status (hp toolbox) and see how many pages your drum has printed. If you are nearing the end of it's life (less than about 10%) you are unfortunately looking at a drum replacement. Since you do have 4 toner cartridges it is unlikely that your toner is causing the issue, this is of course unless it is only occurring in one color.