How do I help my comet goldfish?? I'm so worried ):?

You should just move them into the bigger tank right away. When I was temporarily housing my Baby Common Goldfish in a bowl, she caught a little bit of ammonia burn on her fins and now it has fully healed. What size tank will you be moving them into? They need minimum 40. With a filter. For the fin-and-tail-rot get some MelaFix and add it to the water, and I also suggest getting medicine where it treats all illness even if you don't know what it is.