Neurotic New Fish Tank Owner (What worms are these?!?!)

We just got our first marine tank (60L Boyu) and have been introducing life to it very slowly and things have been going well. We had our water tested four days ago and everything was perfect. So far we a peppermint shrimp, a pyramid snail, two live rocks, and our most recent addition; soft polyp coral (zoos). The worms that are popping up now are FREAKING me out though.



The rock that the polyps are growing on seems to have really long thin worms on it (could these be ribbon worms? Are they safe?) and then this morning we noticed a bristle worm (why are they so scary?!?!) on our one live rock and then another moving through the polyps. The one polyp wasn't looking very healthy, it took a while to start opening and then couldn't quite open properly (The rest have been opening beautifully and seem quite happy where they are) and looked like it had white marks around the mouth where it was battling to open. Is the bristle worm harming our polyps or was it trying to eat something else that could be bugging them? WHAT IS GOING ON?!



As new tank owners, we are fairly neurotic about everything. Our peppermint shrimp molted the other day and we nearly had an aneurysm when we found his husk.



Any advice?