saimus,
Your fish has at least two visible problems. The first is MHLLE. You might want to consider:
In order of what I think is most likely:
Vitamin deficiency (A and/or C); Poor Nutrition; see this reference:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=785228
Chronic Stress
Poor water quality (including high levels of dissolved organic matter and/or nitrate)
Activated carbon (either removing something the fish need or the dust clogging the pores on the fish)
Stray Voltage (is your system grounded properly?)
Retrovirus
Hexamita
Amyloodinium-like dinoflagallate
See this article for more info on MHLLE:
http://reefkeeping.com/issues/2005-06/sp/index.htm
The second seems to be some white and whitish marks on the fish, most of which are at the edges of the fish's body.
It sounds like either a problem came in on the montipora as you suspect, or the fish is suffering from a slow deterioration of health, or both. I suspect at least one of the fish's conditions is chronic, not acute. If you handle the MHLLE concern, the other might clear up.
I hope you did a large water change after the montipora acted up.
:rollface: