Favites receding

[koyfish57]

Hi all, this is a picture of my 40gal aquarium. Over the past 3 days this favites coral has started receding. I’m not sure if the mushroom is responsible, my water parameters are; Alk 9, Nitrate 15, Mag 1300, Cal 420, Sal 1.025 and temp is 76.

 

[RC Reefer 5184]

My guess would be the mushroom or whatever this is circled. I had a hairy mushroom next to a chalice and the mushroom was winning that battle.