Tri color valida

My tri color seems to have lost some of it's bright coloring the last week or so. All the other corals are normal just as bright as ever. I have tested and all levels are normal the only test kit I don't have and have never tested for is magnesium would low magnesium cause this to happen? The only other thing I have done different is I have started to add bakeing soda around a month ago I am useing arm and hammer. any help would be greatly appreciated.
    Thank You
      Bill

 

To maintane alkalinaty. I have been adding about 2 teaspons a week.

 

It has paled and polyp extention is poor. All other sps are bright and happy with great polyp extention. I don't think it is AEFW Wavers no bite marks that I can see.

 

It was magnesium. I got a test kit today and some magnesium and tested and it is way low like around 800ppm so I am going to do some water changes and add the mag tell I get it straightened out. I hope my tri color comes back from the brink. It was doing very well tell I started adding backing soda. I think I added to much at once.

 

Wow I guss I should read the instructions a little better next time. The mag was and is fine I was reading the results backwards. Luckaly the DT's mag is way weak the whole 16oz bottle only raises mag by 24 ppm in my system.