Yup, I've had the same issue a little bit this year. I try to always put them out before a day or two of overcast weather and/or some light rain. The weather channel screwed me on this last batch that went out and I saw a bit of leaf "whiting". Nonetheless, it was only a couple lower leaves and they always spring back within a few days. Generally, I remove the affected leaves after the rest starts growing again. I did notice that if I soak the growth media outside with some nutrients higher in phosphorus and potassium (I use a 7-13-28 that I make), it lessens this effect.
Good luck, sun-scald sucks!