Xmas tree rock friends

[kirstyflash]

We picked up a rock full of Christmas tree worms and have some extra friends. Can anyone please help us with identifying them and let us know if they are friends or need to be nuked.
Pic 1 has something with little striped tentacles poking out right in the centre of the pic
Pic 2 the yellow spongey thing
Pic 3 &4 bi valves?

 

[reef lover]

Mini brittle starfish. Sponge and bivalve

 

[kirstyflash]

Mini brittle starfish. Sponge and bivalve

Thanks a bunch. There are 30+ brittle stars, the lights went out and they came out. The rock was def worth the price tag. There are over 40 Xmas trees, 20 coral hermits, 1 baby Trochus, 5 bivalves, feather dusters and what ever else we haven’t spotted yet.