That is a low-grade rainbow micro lord(acan lord). Wonderful peice! He looks pretty hungry, all lps do MUCH better when fed relatively frequently, like 2-3 times per week.
Good luck, happy reefing and God bless you!
That's a rhodactis mushroom, he doesn't look happy though. He's a bit bleached, I would definitely move it to the sandbed for the time being, Can you post an FTS? What are your lights?
Hmmm... Maybe try feeding the shroom directly? Your lighting is great and placement is as well, the only thing I can think of would be to target feed the rhodactis, preferably in a bowl of tank water with a powdered food and/or frozen brine shrimp. Amazing tank by the way! I love the nems.
First is Micromussa lordhowensis, formerly called Acanthastrea lordhowensis but everyone still calls them Acans. As already mentioned, you can feed the Rhodactis and that should help it recover. Just give it some time they're hardy