Help me ID these “worms”?

[anonymous reefer]

Hi guys. My tank has been running about 3-4 years now. I haven’t seen these worms at all really. In the past few months their population has increased rapidly. Are they bad? I’ve had a few polyps die off on my LPS, but that could be from something else. Are these things bad? What are they?

 

[Saltyreef]

Those are micro featherdusters.

Harmless but may have irritated the euphyllia.
They can take over so remove with forceps as needed. A 6 line wrasse would love to eat the remaining for dinner!

 

[Coral_Wife]

Hi guys. My tank has been running about 3-4 years now. I haven’t seen these worms at all really. In the past few months their population has increased rapidly. Are they bad? I’ve had a few polyps die off on my LPS, but that could be from something else. Are these things bad? What are they?

Is there more than one type of worm here? Or are they all the small feather dusters?
Also off the topic of worms, maybe it's just the pic, but you may possibly have some brown jelly going on where I circled. I recently lost 2 torches and a hammer to brown jelly. I dosed cipro for 10 days with 5-10 gallon water changes every 3rd day and so far have been clear for over 2 weeks with no signs of anything else being affected.