I’m stumped...I just can’t figure out what is going on with my chalice and Favia. Both are receding from the outside edges in. I did have an issue 6 to 8 weeks ago when I had a bad nitrate test kit from nyos which showed low nitrates when it was actually very high. Many water changes later my nitrate is consistently < 20 and all other corals are doing well..including my few SPS, torch, alveopora. My mag level was a tad low a couple weeks ago as I hadn’t been supplementing that..but now it’s 1350 as I hand add it twice per week. Prior to the last six months or so, chalice and favia type corals have done very well in my tank so this is weird.