Ich !!!

Seems he is not eating you need to give him a bath in ICH-X you can also try Para Guard not so toxic you can also try melafix. then try and fined the cause of the ick you will have to evacuate the tank he was in for 45 days as that is the life cycle of ICK. Get a neon goby after as they will pick the ick off and eat it unlike the cleaner shrimp. most of the time the shrimp will only pull it off but will not eat it on ocation and if you are lucky you will get one that eats them.

Bill