I have 2 IRA c5030's that are ghosting, but only on black. No signs of ghosting from any of the colors. The customer has been using a 3rd party toner which I suspect is causing this problem. One machine has ~80,000 pages, the other ~37,000. To test this theory I am switching these machines to genuine Canon toner. If my theory is correct then - have the developers been fouled? Will I need to replace them or is the problem likely to clear up soon after switching to genuine the toner?