Betta Fish: Bloated or over fed?

Hi guys. This is my son’s pride and joy. He loves him to bits.
As you can see he’s a chunky monkey, we think.
In the last month he did have some cotton wool on his fin but we treated that.
We don’t know if he has swim bladder or just obese?
We have tried to see his poo but never see it to check if it’s white?
He swims around quite happily, slight lean at the surface.

For info-

He’s fed pellets 8 a day
Has been on daphnia for a few days
Treated with e-chem for bacteria infection
Tried an Epsom salts bath once he was ok in it just pouted immediately after
His size isn’t decreasing leading us to believe it’s not swim bladder?

He lives in a 5 gallons
Heater 27 degrees
Filter with charcoal

0 ammonia
0 nitrite and nitrate
Ph 6.5
Kh 40
Gh 120

Water changes every week as standard

Any ideas guys?