After I got mine, they took a while to liven up. Found that they like the light, but don't like much flow at all. We try to feed ours whenever we feed the rest, sometimes they take one, sometimes they don't. They've eaten mysis shrimp, blood worms, black worms, and maybe some coral frenzy pellets.
I would def check the flow, bc mine were really ticked about having a tad too much, and as soon as I moved them down a couple inches and next to a rock that blocked the flow, they've started splitting off. Happy go lucky.