Did everything. I did a big water change, bought anti-fungal, and I got some another thing that was supposed to help start the cycle. It was probably ammonia build up, but I am not sure. And also I did remove the carbon.yeah the carbon needs to come out, it'll effect the treatment.
And if it is definately fin rot, you want to stop it before it gets worse. It increases the recovery chances of your fish the earlier you catch it.
If your water is cloudy could it be ammonia build up?? Do you have an ammonia test kit?
If not, i suggest you do a 50% water change, then treat with the anti-fungal (if you are sure it's fin rot)