Yes it's sun burn. You say "started?" Maybe harden off the rest better and/or give the outside ones some shade. In the past I had sun burn almost kill some of my seedlings, but they barely survived.

You might want to review the guidelines for hardening off plants properly to avoid this kind of severe damage from sun and wind exposure in the future.

Dave

I'll find it and read it digdirt. Thanks to you and ed. Should I pinch the daged leaves off to help the plants along?

No, IMO just leave the leaves...whatever green is left on them will help the plants.