Good to know I'm not the only one with antisocial fish..!
I went on the prowl with a flashlight late last night or early this morning and saw the flasher wrasse lurking at the entrance to one of the caves undervthe rock work. No sign of the fairy wrasse but I guess he just had a better hiding spot.
I'm still not sure why they got so timid all of a sudden, they were out most of the time before the new fish so I guess that's the root of it. I just hope they get it out of their system soon - no point in pretty fish if you never see them!