First of all IC's become alot easier if you master everything diddy has in his arsenal. I know it sounds sellfish like I don't feel like putting in details--but really once you master diddy IC's become a matchup he *****. You just need to abuse the bananas, wait for openings and go for the grab. Separating them with grabs is the way to win. If nana is offstage spike her, she's really **** stupid. Just don't let them get the bananas, or else they'll get a grab chances are. Dash attack gets them both above you and free to hit, but if you make a mistake and dash attack their shield consider yourself dead. Use the bananas in a way so if they try and grab you they'll trip. Really limit their opportunities to grab and you'll win, its just a hard matchup until you learn what to do. Ice blocks can really limit your naner game, so take it slow with alot of patience. Once you get momentum they're very much at a disadvantage. It's just a test of if you cant make mistakes. The ice block spam can be countered by repeating a dash attack towards the IC's, but just get close enough to approach them that they'll stop the spam and get worried about close combat and then you can proceed to plucking nanerz.