They look like zoanthids.
You can feed them with Phyto, but I wouldn't worry to much about feeding them right now. Just give them light, and good tank conditions, and they should all open up, and flourish for you. If they don't open within the next couple days, you may have to dip them because they may be carrying a parasite, that is keeping them from opening.
However, zoanthids are typically one of the easiest things to care for in the hobby.
