Sick Betta - need help with Diagnosis

[BettaDad]

I have a Betta Fish that has lost his appetite and energy.... he seems to be loosing the fight as he now also exhibits rapid breathing. He looks like he might be having trouble getting to the top.

Male HalfMoon Betta
1 Month Old (in our house) but younger than my other Bettas in size
5 Gallon Tank - Bio Wheel - Cycled (He is Solo in this tank)
Temp: 82 F
Use API Liquid Test Kit (backed up by occasional quick checks with test strips)
PH: 7.4
Ammonia = 0
Nitrites = 0
Nitrates = 1 PPM
Soft Water
Use Aquarium Salt at 1ml/gal
Use Stress Zyme for water changes.
Diet: Dried Blood Worms, Occasional Frozen Brine Shrimp - refuses pellets

Symptoms:
He has not eaten for 4-5 days.... no interest in food.
I have seen one BM (black ball)
Hangs at top or lays on bottom.
Now has started more labored breathing between trips to the surface.
May have a small cyst (not discolored) on his head on one side above his gill that was not there when he came to us from the store.

I have moved him to a smaller heated tank for treatment - shallower for easier trips to the surface..... no other visible signs so I suspect this is internal.

ANY HELP IN DIAGNOSIS AND TREATMENT WOULD BE GREATLY APPRECIATED!

Thanks!

[Oldfishlady]

How much and how often on the water changes?

I would start by making 50% daily water changes, lower the water level so it is easier for him to breath, turn out the light, turn off the filter, lower the water temp to 76-78F....hold food for at least 3-5 days
If you are feeding the freeze dried type of bloodworms I would stop them and only feed them as a treat 1-2 times a week
You may want to get the aquarium salt out and use epsom salt 1tsp/gal along with daily water changes

It almost sounds like ammonia burns and scar tissue, it could be chlorine/chloramines poisoning, nitrite toxicity, constipation, duct edema or infection .....to name a few things due to his respiration and appetite loss.