Hi, all. Long-time lurker but first-time poster here. To the OP, I am presently growing Bell's, MexiBelle's, NuMex Big Jim's, Long Red Slim Cayenne's, Hungarian Hot Wax's, Jalapeno's, and Bhut Jolokia's, and EVERY one of them that I used foliar plant food on came out looking exactly like your picture does, so I'm going to bet that they've been stunted by fertilizer. It absolutely could be 2-4D damage, but it doesn't look like it to me.
Oh, and I noticed that someone mentioned 2-4D being applied on a calm day . . . you should note the following: on any day when the humidity and temperature combination is sufficient to cause a temperature inversion, 2-4D will lift and drift hours after application, even on the calmest of days. I am located in Arkansas, and we are prohibited by law from commercially applying 2-4D within two square miles of cotton. It is not only a restricted-use herbicide, it is also illegal to purchase by farmers after April 15 each year absent an exception permit.