Acros killing each other/please ID

[Maivortex]

Can someone ID the Acro below the hippo. Can SPS sting and kill one another? This acro just started to touch the coral on the lower right (An ID of this one would be helpful as well) and killed the branch it was touching. It has killed about 2 inches of the coral on the lower right. I have seen sps kill one another in the immediate area of contact but never like this. Anyone experience this? Thanks!

 

[Atomikk]

Sure all the time. Some kill the area that is over 1" long. The first coral looks like a thin branch tenuis. The other one could be an austera. I need a better, pic of course.