1x per week target feeding mysis if you want to
lower light may help but definitly protected from flow
make sure though that their are no rocks or other sharp objects anywhere in it inflation path and that nothing is pestering it. many times LPS's such as a bubble do not open fully because a shrimp, crab, clown or a nipping fish is pestering it.
also there are two types of bubble coral the "pearl" does not have the large bubbles associated with the standard Plerogyra sinulosa