That is what it appears to be. You will know for sure, in a couple hours check again. If it is just lack of water they will start to rise in that time.
I am leaning the otherway, too much water for too long a period of time and a lack of N with all that yellow. You said for missing a day of watering.........one day isn't going to make them look that cupped and lifeless but too much water and the beginning of root rot will. Just my two cents though. Good luck with it............what is your watering schedule?