Pest ID - came from Wellso Brain?

[dollarPit]

https://goo.gl/photos/KNHXmJRhUxckpP4i8

See last picture, can you help id the pest in last picture that appeared after a Revive dip of Wellso Brain... Is this the culprit of my Wellso's demise? I also saved a Favia and had this.

Advise on eliminating others in tank if harmful?

 

[dollarPit]

Note when the Favia had trouble, appeared to be eaten from outside in.

 

[MondoBongo]

appears to be just a standard bristle worm. they're harmless.

 

[dollarPit]

appears to be just a standard bristle worm. they're harmless.

Good to know, thank you!