I posted in the AB thread....I've noticed that when I use stress coat...my bettas shed their slime coat. Also, I have a pet smart betta that sheds his like crazy because he had a wicked case of fin rot. Its all gone but he is still shedding (so maybe I just can't see it).
I would get a heater for his tank.... I'm totally not convinced its parasites. He may just be stressed and treating him unnecessarily could possibly make it worse. My nine bettas guy perked right up with some heat and filtered water...but he never did shed his slime coat (that was my purple guy).
I think it could be parasites, because of him not having any poo and being skinny... those are signs of wasting disease. Also he was very lethargic/draggy at first. Anyway, here's pics of his pink fins if this helps anybody to diagnose him.
Your right, I didn't see that before. It looks like the area around his gills is irritated. It looks bruised. Continue the General Cure, but you might want to throw in some Stress Coat or Kordon's Fish Protector (specifically for bruises/irritated skin)...
If he doesn't start passing normal stool after the General Cure treatment, switch to an oral medicine.