I have had this hammer a long time and suddenly a couple of heads changed looked stressed but the other part looked normal. So my question is if can a coral die partially like the photo.
It can partially die, but that coral is VERY stressed and will likely completely die.
If it was doing well AND growing before and now it is doing this then something has changed and you need to quickly figure out what that is and then slowly return it to the place it was in before.
This is what is so frustrating about growing coral.
I have a hammer colony that had 2 heads shaded, and before I noticed, one head died and the other almost died. Since I moved them, the partially dead head has come back, and the dead head is growing 2 new heads out of it
So yes a coral can live when a part of it die's off, but it really depends on why it died off.