You can tell that you're going to far with brightening your photos when you start to loose detail in your items. Since your products are thin, the edges are getting 'blown out' by the brightening.
If you use GIMP to edit your photos, you get an incredible amount of control over how you adjust them. I made a video about how to use GIMP to brighten your photos without making the subject too bright.:
http://how-to-gimp.com/videos/Look for the video called GIMP Contrast without Blowing Highlights.
Back to lighting...
Direct, noon-ish light will make your pictures look very harsh, and contrasty. You need lots of light if you are holding the camera in your hand to keep the pictures sharp. But, you can get away with much prettier, softer light if you use a tripod instead.
Use your camera's Exposure Compensation setting to brighten up these softer pictures if they come out a little dull.
I always use soft, diffused window light. That means I can't see the sun through the window, and I might even use a white sheer curtain to make the light softer, and more even.
Hope that Helps!!
