Gentian violet is a carcinogen, banned in Canada even for fish use. When it was used, it was an anti-fungal, and not something I would use for a parasite.
Limonene is mainly used as a fragrance - always important in herbal remedies.
Capaiscin is from hot peppers. I imagine the logic is that a burned fish produces more protective body slime, and thick slime can keep Ich from getting anchored in. Salt does this too, but not with the sting I'd expect capaiscin delivers.
Classic herbal garbage. All fish remedies are unregulated and buyer beware, but fear of working treatments has created a big market for snake oil. It's rare for me to disagree with
@Byron , whose opinions I respect deeply, but you still haven't used an Ich medication there. I would try a malachite green formula over heat, but I worked with an importing business where we saw both heat resistant Ich, and an ich-like, white cyst parasite that wasn't Ich, and that moved more slowly (with different cysts). I am not 100% sure that is Ich, but it's hard with a photo.