Ya know, I noticed the exact same thing just last week. I have a Plano filled with just Crappie Magnets. Being that my go to baits are Baby Shad types and Sliders, that particular Plano rarely leaves the storage hatch in my boat. Therefore, I’m not so sure this is a sun problem. Plus, I have several boxes stored in the boat, and I have only noticed it happening to the Crappie Magnets.