Don’t think it looks like dropsy usually looks to me, as this more often affects the body region first with the head being last to see the effects.
Actually looks like when years ago internal pumps had less protection and fish could get sucked up, or their heads sucked into pipe work. I assume that’s not a possibility in a small bowl.
That said, managing water stability in just 2.5 gal won’t be easy but not sure how a single fish would “catch” / come out with dropsy symptoms.