Red Spot On Head

[Sadie555]

Housing
What size is your tank? 3 gal
What temperature is your tank? between 78 and 84 F
Does your tank have a filter? yes
Does your tank have an air stone or other type of aeration? yes
Is your tank heated? yes
What tank mates does your betta fish live with? none

Food
What type of food do you feed your betta fish? Aqueon betta food pellets
How often do you feed your betta fish? usually 2 pellets in the morning, 3 at night. due to a plumbing issue in my apartment, I've had to switch up the routine and I do 5 in the morning Going back to the old routine starting tomorrow.

Maintenance
How often do you perform a water change? once a week
What percentage of the water do you change when you perform a water change? 100%
What type of additives do you add to the water when you perform a water change? Seachem Prime

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? She has always had a light red patch on top of her head, but after the few days being away, I noticed it's MUCH darker red than it used to be.
How has your betta fish's behavior changed? It really hasn't changed.
When did you start noticing the symptoms? Today
Have you started treating your fish? If so, how? Don't know how to treat...don't know what's wrong yet.
Does your fish have any history of being ill? Only due to stress from cleaning the tank, but she's been getting better with it.
How old is your fish (approximately)? It's been about 7 weeks since I got her.

This leads into another question that I have, which is: could the air quality around the tank effect her? Due to plumbing issues, I had to leave (sewage backed up into my bathroom) and although I came back once a day to feed her, I didn't think that the plumbing would effect her. Is it possible that the fumes from the sewage or the bleach used to sanitize my apartment could have effected her?

Or could it be due to stress from the diet change?

I may need a new filter as well (I didn't have the money to buy a new one this month.)

There are just so many things that this color change could be from, but I don't want to change out EVERYTHING out at once. Is it even an issue? Is it a sign of her being MORE healthy?

See why I posted this? :)

[otter]

I think he's probably stressed. I don't think you have to do a 100% water change every week. I don't even do that on a 1.5 gallon. I do about 25%. He is probably having a reaction to the large water changes. Changing all the water might be messing with ammonia and ph and such, which could be stressing him out because of the toxicity. I would do less water changes or change out less water when you do. Also it might help to get a testing kit. They're like 15$ for one with 25 strips. Or at least mine was. My Betta gets those spots too because my ph is extremely high.. 9 which is About 3 points too high and it's pretty bad for them. That might be the problem. Also ammonia.

[Sadie555]

I do have a testing kit. The levels are all fairly higher than they used to be. Should I get a new filter? I already did a 100% water change on Friday. The red spot seemed to go away a little, but now it's coming back again. I hope that I can learn the right way to maintain the water for her in time. It's also REALLY hard to do the partial water changes because I need to scoop her out for a whole hour during the change so I don't hit her or stress her out more.

PLEASE help. How do I maintain a regular water chemistry with a filter, air stone, no plants, and a 3 gallon tank?