I don't think they are starving.
They just have the mechanism to grab anything that first touches the skirts or falls on their disc. Some times they are already fed, and after ingesting, they still try to grab more food when the open again. That's the mechanism and it's a natural reaction.
Yes, most Palythoas and Protopalythoas close up fast when food is offered.
If they won't eat it they reject after grabbing it.
Grandis.