Sick betta, need advice on how to treat him

Tank
What is the water volume of the tank? 5 gal
How long has the tank been running? 6 months
Does it have a filter? Yes
Does it have a heater? Yes
What is the water temperature? 78 degrees
What is the entire stocking of this tank?(Please list all fish and inverts.) 1 betta

Maintenance
How often do you change the water? Once a week
How much of the water do you change? 25%
What do you use to treat your water? Seachem prime
Do you vacuum the substrate or just the water? Vacuum substrate

*Parameters - Very Important
Did you cycle your tank before adding fish? Yes
What do you use to test the water? API freshwater master test kit
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0 - 0.25
Nitrite: 0
Nitrate: 5
pH: 8.2

Feeding
How often do you feed your fish? Twice a day, no food Sunday
How much do you feed your fish? 3 to 10 pellets, depending on size of pellet
What brand of food do you feed your fish? New life spectrum
Do you feed frozen? No
Do you feed freeze-dried foods? Yes

Illness & Symptoms
How long have you had this fish? About a year
How long ago did you first notice these symptoms? Two weeks
In a few words, can you explain the symptoms? Bloating, lethargy, paleness, sinking
Have you started any treatment for the illness? No
Was your fish physically ill or injured upon purchase? No
How has its behavior and appearance changed, if at all? Lays at bottom of tank. Usually dark blue, now pale blue

Explain your emergency situation in detail.
I’m on a school trip and left my betta in the care of my parents. A few days before I left, I noticed his belly was swollen and he would swim up then sink slightly. I thought my mom had overfed him and he was constipated, so I did a day fast and had her give him a pea. He seemed to do better for a week until she said he was laying at the bottom of the tank still and wouldn’t come up to eat. I’m not sure what else could be the issue or how to help him. She called petsmart and they told her to use Bettafix, which she did for a day without telling me. He hasn’t eaten in four days. I’ve attached the pictures she’s sent me. Any ideas on what could be causing this?

 

If already been fasting 4 days, maybe an epsom salt dip for 15 minutes or so can help if constipated,, and feed some frozen daphnia. Works as a pretty good laxative for bettas.

Was thinking possible dropsy, but i don't see pineconing of the scales.

 

I agree with BigmanAquatics, and I also wanted to say, don't use betta fix anymore, it is not medicine, it is just a tonic made of tee tree oil wich can coat the fishes labyrinth oil,

 

I was also worried about dropsy but didn’t notice any pineconing. Some parts of his scales look greyed or loose around his face though, specifically his left cheek and upper lip. That’s why I wasn’t sure if it was just constipation or something else.

Do you have any resources on how to do an epsom bath? I’ve never done one before

 

This is a pretty good article about it.
http://bettasplendid.weebly.com/salt-baths.html

If it is unclear =
Take some tank water out of the tank and measure it. put it in a container where the fish is not going to be able to jump out. Add 1 TBL per gallon AKA 3 teaspoons. If you took 5 cups of his tank water, that is i third of a gallon, and you can add one teaspoon of salt. Mix it with a spoon before adding the fish. Do not add more salt than that, and do not let him soak for more than 15 minutes.
Ideally you can scoop out some of the epsom salt water after 12 or so minutes, and add tank water to reduce the salt before putting him back into the tank and the salt free water so that the change is more subtle.