It's not dropsy. He does appear to be bloated and/or constipated.
Pea should help with that. You may want to limit feeding, especially proteins for a few days. Sometimes porter quality foods can also contribute to bloating and constipation.
The lethargy is most likely because of possible ammonia and nitrite levels. If the tank is new and not fully cycled, I would check ammonia and nitrites daily and do water changes as necessary.
He's beautiful though!