They travel with trips and white flies and even in the air if you have a microscope you can have the certain that this is the problem here.
they best thing to do is to remove the plant or get it far away from the others.
this mites need a vector to infect a plant, so this is why the other plants are ok or at least they dont have the same sympthoms
if you cant see the mites I really dont know what is causing this.