Check your alkalinity first and then magnesium because usually if you have low alkalinity my chalice will show this receed sign before get to my sps/acro
the same thing happened to my BPC Flamethrower. I ended up finding out my hydrometer was out of wack making my salinity 1.022. Needless to say i use a refractometer now. My Flamthrower bounced right back once i got the salinity back to normal. The sooner you find out there better because more of those melting spots will appear.