I've had a 3100cn for 2 years and have printed about 25,000 pages. Suddenly I started getting 2 brown streaks about 1/4" wide on the left edge of the page. This happens on both color and black & white prints. The more pages printed at a time, the darker and wider these streaks get. I reseated all the cartridges but it didn't help. Is this a drum problem or something else? Can this be fixed? Would the drum still be under warranty?