Well a few nights of -7C (19F) is certainly enough to do some damage. Chances are if the leaves had been like that before then you would have noticed. For the time being I'd put it down to the cold and just remove any leaves that don't look like they will recover (if you don't want to leave them to take their chances). If there's still interveinal chlorosis when the soil has warmed up then maybe think about adjusting the pH down a bit. Sorry to hear you're getting chlorotic as well
