Well it's not upset or dead as I get monstrous PE at night and he's been in the tank for 5 weeks and appears to be growing - the picture is on the face that is growing new polyps (started with 2). I'm feeding as well (reef roids and AF Powerfood). My other acans are open and thriving so it doesn't look at all like an acan - never puffs up.
Doesn't look like my other favia which has deeper ridges, but I defer to the experts.
Agree the colors are on the pastel side - probably due to nitrates too low (0.2) - I've been pondering KNO3 dosing. I wonder if this is what young candy cane looks like?
Looks like a Favia that has been seriously over illiuminated. Move it to an area of less intense lighting, and keep trying to feed it, even pellets work but you may have to keep trying.