ET has been sick for a very long time. I have been doing pretty large water changes whenever I can and I have also done a cycle of pimafix. I use aquarium salt as well. His tank mate doesn't appear to have the white spots or fin shredding, but has a little redness in the tail. ET is lethargic all the time. Is there a way to find out for sure what this is so I'm not wasting time and/or money on useless treatments?