Sick Beta (groth on side of mouth)

[hgi]

So this is the lady's beta, I hardly ever really see him as he is in her art-room and she fully takes care of him. Though she brought this up to my attention today, I haven't seen anything like it and he's not able to eat his normal pellets cause of this so she's been feeding him these really small pellets we have. She said it started about a week ago and only gotten worse.

I took the best photos I could, though it looks like a blister.

Tank 2.5g planted,
temp is about 77ish
shares the tank with a bunch of cherry shrimps
I tested the water right after she told me and here's what it was
ammo=0
nitrite=0
nitrate=~5

She doesn't put salt in the tank, though she does treat the tap water with prime when she does water changes (every other day). Any hints on what this might be would be wonderful.

Thanks for looking.

[crazy72]

If it looks like a blister, could it be a burn on the heater? (is there a heater in this tank?).

If you have almond leaves, you could put a couple in. They are said to do wonders for bettas.

Disclaimer: I don't have a clue about bettas.

[hgi]

There is a heater in the tank, and a burn was my only guess... I was going to add that nothing has been added to her tank in a long time so it's not like there was any huge changes. If it is a heater burn what should I do?

[crazy72]

Salt is usually what comes to mind. I believe bettas are fine with a bit of salt. I even think they like it. betta water

Otherwise almond leaves for sure, if you have some.

[Sandy Landau]

It is hard to tell with this photo but could it be an injury? Looks like a cut to me. I would put in some Tetra Lifeguard to keep it from becoming infected with bacteria or fungus, and this would also treat it if it is actually caused by an infection. One half tablet dropped into the 2.5 gallon tank, once per day for 4 or 5 days would be helpful I think. I have tried that medicine on my betta with shrimp in the tank and the shrimp were fine too.

[hgi]

Update,

I've told the gf to add salt, 1tble spoon then 1/4tble spoon a week later when she did a water change.

The growth has for sure gotten smaller and much better looking, thought there is still a slight small problem when it comes to feeding. She feeds him once a day, he's been eating these pellets that are half the size of the pellets he normally eats and for the last two days he's been chewing on them then spitting them out...?

I'll try to get some photos when I get home from work today.

[roadrunner]

Salt is good for short term using to use as a treatment, but I would not recommend it for a long term use. From the photo is hard to tell. Maybe he just scraped himself agains something sharp. Could you check all decoration in the tank for sharp edges?
Also I was wondering if you check the water temperature when you change water. It should be same or within 1 degree of the current temperature in the tank to avoid shocking the fish. And how much water do you usually change? 20-50- 100%?
As for food, maybe you can try something even smaller if he has hard time eating. If he spits them out, it's ok as long as he is eating a little bit.