You wrote-"WATER TEMP IS 70 AS ALWAYS". This, the usual water temperature, is actually a fundamental problem for your betta. Bettas require a steady water temperature of 80f degrees in order to thrive so what I recommend be done in order to fix this is add a water heater to the tank and gradually raise the temperature to 80f degrees and keep it there. The proper water temperature will greatly help the fish feel better.
In addition to adjusting the water temperature I'd suggest adding some aquarium salt to the water, add 1 teaspooon.
It would also be beneficial to the fish to change 1 gallon of water once every 5-7 days whilst adding the corresponding amount of aquarium salt which would be a little less than 1/2 teaspoon.
It's also important to not overfeed the fish. Feed only a small pinch of food once a day.
I'd continue treating with BettaFix as you've had some success with it. Keep treating for the next 2 weeks making sure to follow the directions on the product label.
Try to avoid adding excess products/water conditioners to the fish's water as they can intoxicate your betta. Aside from the BettaFix and aquarium salt you should only be using a dechlorinating product for new water that is to be added to the tank.
I believe by rectifying the water quality issues in the tank your betta should bounce back to normal assuming it has not been too profoundly affected.
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