Swim Bladder Problem

[-FighterFishh]

One of my male endlers in my 30L tank seems to have a problem with his swim bladder.
He doesn't seem able to swim in a straight line, and from his gills to the start of his tail seems to have lost colour. He also seems to sometimes just stop and chase his tail. I'm not sure if it's because he's lost control or something, but it's really strange.
I've ruled out my betta hurting him as he doesn't have any injuries on him, and Chai doesn't take any notice of him anyway.
If this is a swim bladder problem, what can I do to help him? If you think it isn't, what else could it be, and what could I treat him with?
Any help is much appreciated!
Thank you!

 

[soybean]

This happened to all of my endlers after I'd had them about a year. Went from 8 to 2 in a fortnight. How old are they?

 

[swanseastilo]

How do you know if its got swim bladder. My angel always swims a little to one side.

 

[-FighterFishh]

This happened to all of my endlers after I'd had them about a year. Went from 8 to 2 in a fortnight. How old are they?

I'm not really sure. The other 5 are all fine, it's just this one boy. My 3 endlers upstairs are also okay too, but I'll keep an eye on them all.

How do you know if its got swim bladder. My angel always swims a little to one side.

I don't really know he does, I just presume he has, since he's always swam normally and has only started swimming strangely like this today.