it seems like they got tanggled, like too many tentacles got involved in grabbing a food or something .. usually, if it is tanggled, it will return to normal state soon within 2 days .. if it got trapped by something more serious than food, like power head, it will take longer. I have mine before that somehow manage to tie a knot on it self .. so it cut itself (yes, detacth the tanggled section) to free it.
If none of the above apply, there is something in the water that caused it .. Some people may say your salinity is a bit low, but in my experience this anenome can take .020 salinity .. but .023 is better .. raising yours may not be the answer if it has been there for 2 weeks with the same level.
In my experience, there is a product out there (ex: for filter feeder food) that can caused the anenome to deflate .. so trace back what you did before you notice the changes.