Wonky Betta

hey guys, I was recently given 3 Bettas by a lady who was getting out of the hobby. She had kept them in TINY tanks (I’m talking like 700ml or so which is like 0.2gal? Literally the size of the cups at pet stores!)
Anyway, they’ve all got a bit of a kink, which I know isn’t really fixable. But one of them is also wonky... like as in, he’ll swim/rest on a bit of an angle... this is a terrible photo (but he’s so hard to photograph!)
When he swims in a straight line, he straightens out, but when he turns or rests, he goes on this weird wonky angle! Any clues what causes this/if it can be rectified? Would exercising him somehow help?

 

It looks like swim bladder disorder. Can we get more information of his current tank? How big is it? Is it heated? Temperature of the tank? Is it filtered? Do you know your water parameters? And more pictures of him please.

 

Ok thanks, I’ll look that up.
I’ve only had him for about 3 days, he was like this when I got him. I know his old tank was heated, unfiltered & about 0.7L.
He’s currently in a 10L heated (25C) unfiltered tank while I sort out something more long term for him. I don’t know water parameters, as I’ve not tested. I’ve been doing daily 25% water changes as it’s a new tank. Bear in mind he’s been in this tank for 3 days & his condition hasn’t changed in that time.

 

It's hard to know what is causing it, so I would just keep him in better conditions and see if he changes. I think it could've been caused by poor water quality, pH or temperature shock, poor diet, or some sort of physical injury to his swim bladder. It doesn't seem to be severe, so he shouldn't be affected much by it.

 

Thanks Repolie - any of those could be it! I know the lady used to take the fish on holiday with her in plastic containers with no heaters, so temp shock is possible. She also used a PH-neutraliser & aquarium salt. Given how small the tanks were, poor water quality is possible. I have no idea about swim bladder, so will try the recommended treatments google has shown me...

 

Ok a little update: so Kingsley seems to be having good days & bad days. The treatment I found for swim bladder was just to fast the fish for 2-5 days, then feed it some pieces of pea. I did this & fed Kingsley only peas for a few days, giving him 2 ‘Betta pellet’ sized pieces of pea every morning & one bit the same size at night. He seemed to slightly improve, but still often rested on weird angles. I’ve been feeding him per normal the last week or 2 (2 Betta pellets in the morning, one at night if I remember!) & have occasionally swapped a Betta pellet for a piece of pea or a blood worm. The last 2 days, though, I’ve often found him resting on the bottom of his tank like in the pictures below, not in the roots of the plants up the top of his tank like he usually does. Pretty concerned about him!
He does still swim ok (like when I fed him this morning he was onto that food quick as a flash), but he just looks so wonky!
Also noticed he’s got translucent white stuff coming from his butt? Is this a sign of constipation? The solution for this is feeding peas, though, right? But I’ve been doing that for like 2 days already?

Sorry for the super long post, just trying to figure out what I can do besides feeding him peas since that’s not working!
Water params have been consistently good when I’ve checked & I’ve been doing consistent partial water changes. I’m due to do a ‘vacuum’ this evening, so excuse the state of his tank right now!