I have a few gorgs and have one of the same type that you are calling "blueberry". It's polyps are always open and I believe feeds ok however my biggest issue with it has been the fish and hermit crabs eating the blue flesh on the stalk and chompimg down the polyps.
Other than that it's been doing well but I am afraid there won't be much left of it pretty soon. The fish that really munch on it are my coral beauty, yellow tang, yellow tail damsel, blue tang, foxface, and as mentioned hermits. If you have any of these in your tank it makes for expensive fish food.