First, peas are an old remedy for bloating in fancy goldfish, it doesn’t work on any other fish. It’s just gotten misapplied all across the internet.
Epsom salts has some benefit for constipation, when fed at 1% to 2% of the diet by weight. Soaking food in it doesn’t work, you need to bind it with the food with agar or gelatin…otherwise it just rinses right off.
These internal issues are tough to deal with: this could be a protozoan issue, constipation/blockage or even nematode worms.
Binding metronidazole in the food at 1% can help against protozoans.
How long have you had this fish? It’s pectoral fins look cloudy and possibly spotty - do they look like that in person?