I had this happen with a salinity change problem but all came through. It lasted almost a month though. You did not change salt recently did you?
Otherwise just watch them and ride it out. You might check the tank and make sure nothing is pestering them.
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,