Looks like it could be a feather duster, hard to tell, I have a 6 head torch and not specific to any one head, but 1 will close for a day and open the next, then another one will a week later. It's usually a natural instinct for them to do that. They will also spell chemicals at the feather. Not sure if it will end up killing it but if it is opening up it should be fine. If it stays closed for a 48 hours then you got a problem. But feathers will grow constantly in the tank everywhere if you don't have something that will eat them. They grow in low light places so it would surprise me you will have many more growing in and around that area as well as other places in your tank