PBTs (Powder Blue) are ick magnets. This is very well known.
So at this point, if it is not eating, you have to take him out and place him into a quarantine tank. If you don't have one, or don't know how to set it up,
look here.
Since it is covered with ick, and is in a QT, use 3/4 of the recommended dose of copper. Make sure you monitor ammonia levels, as you will have to do water changes ever other day or so.