Spishkey
Spishkeys Turtle Rescue
ok sorry if youve mentioned them before but what are your water stats? (ammonia nitrite and nitrate?)
this is a long shot but i think you are looking at two other potential causes here...
1. it could be dropsy. featherfins are a scaleless fish so you wont see the usual pineconing like with fish with scales. dropsy is a symptom of a bigger problem so it could be a bacterial infection or water quality issue? dropsy in scaleless fish appears as a bloating look, swelling underneath the fish like a big clear bubble.
2. i cant recall the scientific name from the top of my head but it could be gas bubble disease? do you do water changes straight from the taps (mixer taps are the biggest culprit of this i have found?) if you google gas bubble disease and supersaturation, it will give you a little more info on this (sorry i would explain but its early morning here and i really do need to get some sleep. if theres no replies here when i wake up, i'll write you a brief sum up of the causes and symptoms etc
basically its to do with gases trapped in water getting into the fishes body, then trying to release itself and appears as bubble type things on the skin? you normally get other symptoms too such as gasping at the surface and/or awkward swimming....so im putting my money on dropsy for now if its not a tumour or growth 
this is a long shot but i think you are looking at two other potential causes here...
1. it could be dropsy. featherfins are a scaleless fish so you wont see the usual pineconing like with fish with scales. dropsy is a symptom of a bigger problem so it could be a bacterial infection or water quality issue? dropsy in scaleless fish appears as a bloating look, swelling underneath the fish like a big clear bubble.
2. i cant recall the scientific name from the top of my head but it could be gas bubble disease? do you do water changes straight from the taps (mixer taps are the biggest culprit of this i have found?) if you google gas bubble disease and supersaturation, it will give you a little more info on this (sorry i would explain but its early morning here and i really do need to get some sleep. if theres no replies here when i wake up, i'll write you a brief sum up of the causes and symptoms etc