I suspect the first is Asterina stars and the last is a microbrittlestar.
Personally, I would keep both (assuming these are the correct id).
The brittlestar for sure.
And I personally believe the majority of Asterina stars are beneficial as well. Now and then there can be problems (eating, in particular SPS corals) but I would expect you to get these on SPS coral frags. I would keep all of these.