Is this a tumor? (Swabwa barb)

[Fruity fish]

Hi! I have a community tank, one of the shoals I have in here is some Swabwa barbs. Unfortunately, two of them (the other barbs are well behaved!) seem to be stealing food from others and eating too much. I'm working to find a balance, but nonetheless--because of this they tend to look a bloated.

Today I check on them and noticed this strange swelling on one of my barbs undersides. it is very odd seeing as its only on one side and is closer to his tail than is stomach. is he just bloated or is this a tumor or something? I have no idea how to help him-- I would really appreciate another opinion.

Here's a picture, I'm not really sure how this works so I'm gonna link it

https://drive.google.com/file/d/1QY5yBH8qrXipVEMYkTCSzkV4tUfxE7MC/view?usp=sharing

 

[Autumnsky]

Hello and welcome Fruity fish,

The fish are very pretty. Do you know if you have males and females? Sometimes the group of fish, made up mostly of males will chase around and spar for the attention of females, or if there are not any females just bug each other and can cause extra stress.

How long has this tank been set up?

Do you know your water parameters?
Ammonia
NitrIte
NitrAte

pH

GH / general hardness

KH / Alkalinity / calcium

TDS- total dissolved solids

water temperature
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How long have you had these fish?

Are you familiar with the nitrification cycle? The article link in my signature has a lot of good information plus info on building a BB / beneficial bacteria colony in your filter and tank so you can keep the parameters safe and fish happier.