Nutrient burn... As long as you flushed and the new growth isn't curled under you are on the right track to quick recovery.
I don't understand the reference to an upside down taco tho... It's more like a claw fingernail curling under like the other guy said.
Go much easier on the nutrients next time, you can't force feed a plant all that happens is you burn them and stall growth. Also if you are in pre-nuted soil you shouldn't add nutrients until around 2 months into the grow and then only in smaller doses until you see how the plant reacts.