Stronger lighting would definitely help. Get two standard reflectors from Home Depot (or wherever) and two 6500°K CFL bulbs. That should provide all the bright daylight you will need.
White balance. Make sure it is set correctly for the light you are using - daylight, fluorescent, whatever - or use the custom mode and calibrate it against a piece of white paper placed in the field of your photo.
Focus. Once you have enough light, be aware that the field of focus extends much farther BEHIND your focus point than it does in front. Also, the depth of this field is much narrower in macro (closeup) mode. In general, if you focus on the point CLOSEST to the camera, everything behind it will be in focus. If you still have trouble, you might back out of macro mode and use your photo imaging software to get a larger image - ensuring that your initial image is set to maximum quality for your camera (300 dpi or better) so that you can enlarge the image without losing quality.