Hopefully these things aren't bad as they are all over the place.
They are little white tubes on the rocks and have what look like single white hairs coming out of them. It looks like there are black rings on the hair as well.
Photos are blurry, but they look like vermatid snails to me, more of an annoyance than an actual problem. A dot of superglue on the opening to the tube will take care of them though
Do spaghetti worms sting corals? I've got these things all over the sand in my 10g and have had a hell of a time with my corals in that tank. Noticed a few of these critters are pretty close to the places where my brain has been losing tissue and wondered if they are the culprit?
They don't sting corals. They can be harmful if they become too abundant and irritate the corals. You especially see this with zoas. Sometimes you'll get a ton of spaghetti worms in between the polyps, and since the worms are always out, they keep the polyps closed up.