Betta help?

[Psylk87]

MY betta isn't eating and has been acting strange. He is two years old (that I have had him). He has always been an eager eater but hasn't eaten for the past 2 days. He is also favoring one corner of the tank which isn't normal for him. He has never been sick in the past. He hasn't been rubbing on anything or acting odd any other ways. Water levels are all normal and good (did an API test and everything is within the right levels). All other fish in the tank seem fine (Neon Tetras, Snails, and shrimp). He is the only acting different. He looks normal to me but maybe I am missing something so I am adding pics. The only recent change to his tank has been a female RCS eggs hatching and a new filter (seeded with old filters media). Could it maybe just be bloat from eating too many babies? Or maybe the flow on the new filter is too much and I should try baffling it? Maybe even constipation? Any advice or help is greatly appreciated.






Please ignore the diatoms. The snails normally sit and eat off that leaf so I never clean it.

Also where do you guys stand on Bettas + Melafix and Pimafix? Should I maybe try salt? If so how much (tank is 10 gallons). I have no clue what to do for him. Any opinions or thoughts are greatly appreciated I am kinda worried about him.