I'd check my water quality first and foremost. It needs a lot of Calcium. If it's in your reef tank this shouldn't be a problem for you but I'd check the Calcium, Alkalinity & PH first off.
IME: I don't think high light is much of a requirement. It likes to be in a moderate water flow.
If you remember the ball I have in that little 10 gallon of mine. It's been in there for months and it only has a 15 watt standard output fluorescent and a small hang on power filter that dumps the water right thru the Chaeto. This is my most neglected tank because all that is in there is Macro Algae, but I keep the water quality at reef chemistry.
Good Luck. If you need some more, let me know.