The Clownfish should be okay. It's unlikely the parasite will move to them.
Cleaner Shrimp eat parasites off of fish. Do CS eat parasites off of other CS? I don't know. An isopod is much larger than their usual fare.
I suspect there are no parasites on the Clownfish so the CS must eat fish food. When the discussion moves to food my pat answer is pretty well known: Feed algae and frozen meaty foods with algae. Even clownfish need to eat some algae. My favorites, in no particular order, are GSL Brine Shrimp, Emerald Entree, Rods Food and BSD Enriched Brine Shrimp. Mysis Shrimp are okay but lack algae. A variety of foods is best.
Aloha