Its a hider so pics are tricky. This is a fish that was getting picked on badly when I purchased it. It was getting eaten on by red tailed sharks and Chinese algae eaters. When it came home it looked to settle in but then it started to shed skin. Then it went through the Ich treatment when the clown loach was introduced and its been a bit off ever since. But this thing has been skinny from the get go.Do you have a pic? Like @sir_keith said it could be age. Other (unlikely) possibility is parasites but then other fish should have symptoms too...