I've never heard of mold growing on fish scales. I still can't think of what could be causing that smell either. I'm sorry I'm not being helpful.
I'll keep trying to hunt something down but just don't have any more ideas right now.
Did you try asking in the health section. Is it possibly a type if velvet or something? (Thankfully I've not had many health issues over the years, but that means I'm not one to ask either).
Anyone else? Please hop on and offer any ideas. I'm sure jadaBlu would appreciate it.