Tissue loss on montipora setosa

[stinkyfishy710]

My montipora has turned white on a few spots around the edges. Have had it for a while and it was doing fine. This is the only sps I have. I’m thinking maybe to much light but not sure.

 

[vetteguy53081]

Some causes:
High alk
Too much light and/or water flow
Monti eating nudibranch
High nitrates
Low calcium
Low salinity

 

[stinkyfishy710]

I use Red Sea coral pro salt and do weekly water changes, this is my only sps and all my other corals are small frags so my calcium and alk are pretty stable the salinity runs around 1.026. I haven’t added anything in a while so I don’t suspect nudibranchs.Could really low phosphate and nitrate cause it when I test for phosphate I get no reading (salifert test kit) same for nitrate but I test nitrate with api so it’s probably not very accurate.