First attack on San Carlos on the morning of 21st May 82 was against HMS Argonaut by an Aermacchi using Cannons and Zuni Rockets. I suspect most of the Zuni's the Argentinians had were on the Islands for the Pucara's and Aermacchis to use and that the only Fast Jet attack aircraft they had that could use them was the Skyhawk. One of the Argentinian forum members like Marcantilan or CAW may know what the reasons were.
FIRST CONTACT: HMS ARGONAUT OFF FANNING HEAD - Maritime Prints