I am not an expert on discus and clown loaches, other then knowing a lot of people who keep them together. But I do know that if you increase the temperature high enough you can kill off white spot because it becomes to high for them to reproduce, and for sensitive fish like discus and loaches it is a safer way to get rid of a white spot infestation.
Also there are two (ish) theories about white spot, one that you introduce them with fish, then if you treat the properly you can get rid of them out of your tank completely, the other one being that white spot is always dormant in your tank, and it takes some trigger (stress usually) to have a white spot out break, there is not proof that I have managed to find proving either way being true.