My bta decided to be a donut. Water parameters are pristine, calcium 400 ppm, mg 1580, alk 4.5/12.6.. Sg 1.026. Tank is stable.. Did a 40% wc trying to "help" the bta.. Tank has been established since 2006.. Is it normal for them to donut? It refuses to eat now and after the wc, closed up, no sign of tentacles.. Not moved, likes its spot stuck to lr.. Ideas? Lighting is moon led and 10000 daylight ho with actinic lighting during day.. It hasn't moved in 6 months and has grown. Never donuted out that we seen before..