HICA is good but I would still advise you to stick with Leucine. You really want to look in to something that can help increase your appetite and to be honest the only real products that do that at all are generally going to be test boosters. If you have a higher test level it generally causes you to want to eat more. You would want to do research on any product recommended as to how it would interact with your Cystic Fibrosis, but look in to some DAA products like Intimidate SRT and some Fadogia products like Tropinol XP. Those are good places to start with in terms of increasing your desire to eat.
Aside from that you simply just have to force more calories in. That is really pretty easy to do if you can eat as much as you do now while supplementing with liquid calories like protein. I would suggest 100% Whey Protean or Isotean (vanilla is my favorite). Although you can really just pick any protein that has decent reviews and buy it. The real goal for you is to just ingest more calories. So those two things a t booster and more protein will hopefully help you to do that.
For quick foods:
Yogurt (greek preferably but any kind will be fine)
Drink a shot of olive oil every day or night before bed this is a large amount of calories very quickly and doesn't taste as bad as it sounds
I am no doctor, so make sure anything recommended in this thread you research to prevent health conflicts. The food part is easy though just keep some of those things I listed and drink more milk with protein shakes. Also unless Glutamine has some benefits for your specific situation it isn't necessary.