I would give them live food only. We never use frozen foods unless we the fish is health because out fish usually die from gram-negative bacteria within a few days of feeding. When they are well, give them what you want.
If the edge of the fin is black or red-brown then you have fin rot. Add some Indian almond leaves, keep the temperature warm, water clean, and use diet of live food. I'm not a fan of the treatments because they tend to include things that make no sense to me. If the edge of the fin is white, then the fin is regrowing and you need to take no further action. If the edge of the fin looks like cotton wool, then you have a fungal infection. Use a treatment of your choice. If it looks clean, then you either have a fresh and clean tear, or a congenital deformity, then you don't need to take any further action. I hope that helps. I know that a lot of people get confused about what fin rot looks like.
Zozo - as usual, I strongly agree with you. Clean water and excellent food (something aquatic and alive that will linger around - daphnia would be great).