Angelfish Problem

I have had an Emperor Angelfish (juvenile) for about 6 weeks and suddenly he
is looking pale and not eating too well.  The other fish in there (maroon
clown, foxface rabbitfish, hippo tang, blue-chin trigger) are all seeming to
be fine.  I checked salinity and it was pretty high; could that be the
problem?  If I bring the salinity back to normal, do you think he'll revive?