I think KiwiGal77 is on the ball with this. The filter hasn't developed and the fish is probably suffering from ammonia poisoning.
Do a big daily water change for a month and see how it goes.
If there's no improvement after a few days of water changes, let us know.
Don't touch the pH. Bettas come from acid water so leave it alone.
Do a big daily water change for a month and see how it goes.
If there's no improvement after a few days of water changes, let us know.
Don't touch the pH. Bettas come from acid water so leave it alone.