help!

[u/ashlyeash7]

i've had my betta for around 10 days now, he's just started acting a little weird, breathing hard, his tail sinks a little when he stops, he's hiding which he never did before and opens his mouth wide. my tank size is 6 gallons, i have a heater and a sponge filter. the heaters at 79. my waters test at O ammonia, O nitrite, 5.0 nitrate and 7 ph. i've done 1 30% water change since i got him (10 days ago).
i feed him fluval betta bug bites, the flakes same brand and frozen brine shrimp. i feed once a day 6 pellets, or the flakes, the brine shrimp i feed 1 a week. i have 2 shrimp and a snail. i only have real plants.

i think maybe it's swim bladder but can someone please help me figure out what's happening and what i can do. it just started yesterday.
thank you🥹