Hey martin
If the parasites are actually oodinium, they belong to the group of dinoflagellates. Some of these actually do have the ability to form a cystic stage which can survive conditions the living microbe could not. Therefore and since you probably won’t be able to exactly determine what species you’re looking at, it is a good idea to wait a few days under normal conditions and then rise the temperature again.
I would go back to normal temperature for some days and then rise it again for maybe one week or so. Then I would again just watch very closely at the animals the consecutive days… if something should have survived just redo it…
My experience (not with paros) is that it can take up to four such cycles…
Greetings Rafael