I have had my blonde naso tang for about 6 weeks and I added a yellow tang that is healthy as well about 3 weeks ago. Today I noticed my tangs swimming as if something was bitting them. I noticed them hanging out by my cleaner shrimp. They have no white spots on them so I am hoping they don't have ich. What I noticed is them darting and sharply turning in the water as if they were scratching against the rocks but they did it in open water. Also as they swim they may twitch. My naso normally picks at everything as if his appitite is never satisfied but today he hasn't been nibbling at anything. My yellow tang is normal and and his behavior hasn't changed other than the erratic swimming. What could possibly been wrong and how should I proceed and what should I treat with? Thanks