Help not sure what this is?

[Mdj]

Over the last month I have been working way to much and noticed that my zoas are slowly melting away today I had some time and noticed something strange growing on frag plug with them and appears to go under plug as well. Does anyone know what this is and what I should do about it thanks I believe the last pic is a colony of green hydroids please corect me if i am wrong thanks

 

[ramseynb]

I'm not sure what I'm looking at in the first two pictures. The last picture is hydroids.

 

[thinhn1]

Colonial hydroids, get rid of them!