I was going to suggest mild 'leaf scorch' because I get that Silvery condition on some on my young seedlings as I transfer them from inside under lights to greenhouse and then to outside in the garden. Each time the light becomes more intense. If the change is accompanied by bright sunlight, it can happen in less than a day. And it doesn't have to be hot sun either---just very bright sun. Never known this to cause any permanent damage to the overall health of the plant other than temporary unsightliness. In fact, the damage area will try and repair somewhat back to green. Here are a couple pictures I took earlier today of the silver leaf condition I'm talking about. Pictures are not good quality.
