Do you have a pic of it? I have a nice closed brain too that I've had for about 6 months. I've had my share of problems with it. It was doing great at first and then a big patch in the middle bleached over-night. I thought I was going to lose it but then I isolated it by itself on the bottom a little better and the area came back. Now the whole tank is struggling with bryopsis and I've been doing everything under the sun to get that under control. The algae grows around the edges of the brain now and it's pretty frustrating. I just have to pick it up once in a while and tear the algae off.
They are really mucusy (if that's a word) corals. Mine releases a lot of stuff when I mess with it or try to feed it. I've never seen it extend sweepers to eat, although I've tried feeding it different foods. It loves when I stir up detritus around it. The cloud goes over it and the color gets a lot more brilliant for a while. I don't know whether it's eating it or not. I assume it is.
All I know is, I've seen some really nice ones on here to know that mines doing ok but it must not be thriving. It doesn't have near the color as a lot of them I've seen on here and I really haven't witnessed much if any growth at all. GL with yours.