Euphyllia Paraancora bleached out

[osk4r]

Hi, please help with my euphyllia paraancora which has been faded for over 2 months. The aquarium is 64 liters, more than 2 years old. In the filter panel about 1kg of MaxSpect BioBalls. Every week I change about 15% of the water with Red Sea Salt. I try to keep the KH around 8, Ca over 400, MG over 1300. The coral is not pulling polyps but there is no excessive tissue loss. You can see that small heads are trying to grow from the sides. ICP showed nothing out of the ordinary. I tried moving it to another location but it didn't help. What else can I try?

 

[twentyleagues]

Lighting and /or nutrients.

 

[osk4r]

Lightning is Ai Prim 16hd. I don't measure nutrients. I always have trouble reading the colors. Only PO4 from ICP. I forgot to mention but the rest of the collars look ok, including two euphyllie glabrescens