It's hard to tell why this happened - but I don't see more than a couple of leaves affected - most of them look just fine! My inclination would be to think you spilled some water on them and they burned from the light... Personally, if this was my grow, I'd trim off those few leaves and forget about it!! They're not going to do the plant much good ... just be careful to water/feed the soil only!
Good luck... the grow looks great aside from those couple of leaves!