Grey marks on favia coral

[Grizzly_Jordy]

I have this favia coral that didn't have these grey marks when i got it but i noticed them today could this be from sweeper tentacles from other corals? I used to have it placed next to a maze coral but one morning noticed the sweeper tentacles could this damage be caused by that?

 

[Timfish]

Looks like some dieoff. Could be differences inwater and light parameters bewteen the tank they grew in and the tank they're in. Could be shipping and handling stress. Could be from getting stung by another coral at some time recently.

 

[mtraylor]

Yes it can be from sweeper tentacle from other coral. I see the sweeper in the pic you posted.