Possible fin rot, raised temp, now strange behavior..

[gmyers0203]

I've attached some pictures and filled out the form below.

Essentially, Sulley was showing signs of possible fin rot and then formed a small raised black spot behind his right eye. We went to Petsmart to buy some medication but were told by the associate there that the fin issue was likely due to a lower water temperature (76*). They also stated that the black spot was likely from him bumping his head somewhere. The associate suggested buying an alternate heating source to raise the temperature further as bettas do better around 80*. I had a heater with a preset thermostat to 78 but only raised the temperature to 76*. So I replaced the preexisting 25w heater with a 50w adjustable heater. The temp has been raised and the black dot has disappeared. However, Sulley has now been laying on the substrate more than I've ever noticed before (pics attached). Could this be a sickness setting in or a reaction to the temperature change? Any help would be greatly appreciated!

Housing
What size is your tank?
- 5g
What temperature is your tank?
- was 76 up until yesterday. Now 80
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?
- One black nerite snail

Food
What type of food do you feed your betta fish?
- Alternate between Betta flakes and Bloodworms
How often do you feed your betta fish?
- Once a day

Maintenance
How often do you perform a water change?
- Approximately once a week
What percentage of the water do you change when you perform a water change?
- 50%
What type of additives do you add to the water when you perform a water change?
- Seachem Neutral Regulator

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

Ammonia: <.25 ppm
Nitrite: 0 ppm
Nitrate: 5 ppm
pH: 7.0
Hardness: unknown
Alkalinity: unknown

Symptoms and Treatment
How has your betta fish's appearance changed?
- What could potentially be fin rot and yesterday he had a small black spot (raised) near his head (The spot has since disappeared since we raised the temperature.)
How has your betta fish's behavior changed?
- Has not been as active and I have found him laying in the gravel several times hardly moving, but appears to be breathing normally.
When did you start noticing the symptoms?
- Fin rot was noticed a couple weeks ago. The black dot was noticed yesterday.
Have you started treating your fish? If so, how?
- After taking a trip to Petsmart with the intention of buying some medication, we returned home with a stronger (adjustable) heater after one of the employees stated that the deterioration of the fins is sometimes related to lower temperatures. We raised the temperature from 76 to 80 over a couple hours. As of this evening, the black dot is gone (it was there this morning). However, it appears that the increased temperature has potentially affected his behavior. Or he truly is sick and is starting to show more symptoms. *This evening I did add 2 tsps of aquarium salt*
Does your fish have any history of being ill?
- No
How old is your fish (approximately)?
- Bought him at Petsmart approximately 3 months ago

[Oldfishlady]

I would make a couple of 50% water only changes for a couple of days and see if this perks him up...it may have been something toxic that got in the tank either from the new heater or your hands....

Keep us posted....