frogspawn dying

Recently I did some changes on my tank. I sold lots of colonies and kept only some frags because I did a layout change. I changed all my rocks and switched from a calcium reactor +2parts to 2-part dosing only. I had some parameter fluctuations, so I was expecting losses. I have stable parameters...

My 16 gallon reef has been stable for the longest time, until I got bubble algae and started to increased my water changes which got to a point where my nutrients were too low and now I have dinos. I had dinos about three weeks before I decided to do a blackout and all of my coral was fine, but...

One of my recently new frogspawn frags hasn’t been fully opening up for the fast few days, and it seems as if one of the heads is receding/ dying. I was wondering if this was BJD or soemthing else?