Monti cap going white ish help

[saltlife97]

Hey guys my montipora has been slowly getting white and not opening , my parameters are stable and have been but let m elbow if you have any on-site into why this is happening , happened again about a month ago and recovered but now it is going through it again , not sure if it’s a film , I’ve blown it off but I don’t see the colour coming back and extension of polyps

 

[shakacuz]

did you test the water after a few days of the monti doing this, or immediately when you saw its color change again? usually when we see certain corals change like this it's due to a swing/change in something. have you change the lighting? any other changes/additions you've done over the course of time before the monti begun to do this? new salt? have you done an ICP test to see if you're lacking certain trace elements?

 

[Stang67]

Calcium and mag a bit low and alk a bit high. When was your last water change and what salt do you use?