Physan is not organic.

Sulfur will not cure anything, rather it is used on cuts to prevent any possible fungal or bacterial attack.

Sulfur dusted on the plant can prevent fungal infection. I've used it to prevent further spread on a tree and it worked. I have also dusted it on my orchids when there has been bulb rot. It seemed to work after cutting away the bad part, then dusting.

Spraying water on the plants is not going to solve your spider mite problem. And as you can see, all it does is cause more problems. One somewhat efficient (though time consuming) method is to wipe down every single leaf, one by one, with rubbing alcohol. I had to do that last month when I found spider mites on plants, since I couldn't find any miticides at all here. I did that 3 times, a week apart. It wasn't a bad infestation, so seemed to have worked pretty well.

As for the fungicides, if you can't find any of the products suggested here, just go see what is available at a local store. Generally anything that is safe for roses is safe for orchids.

Hi All
Noted and I will try those recommended method.
BTW I don't think I can wipe every leaves of my orchid as I have 100 pots of orchid. Anyway thank you very much for your suggestion.

I wiped down something like 40 plants, which was already quite a job! Luckily I didn't have to do all my plants, the group living on the windowsill was fine.