looks like feather duster and sponges to me with out seeing a clearer image but if thats the case you have nothing to worry about. I have that same sponge in my tank and they generally grow in dim areas which is nice.
I can see them looking more like the hydroids than anything else but still not 100% sure that's what it is. They are brown tubes that are kind of hard but nothing ever comes out of them. They just keep getting longer