check into a
quarantine tank because it will become one of your best investments in the future.
it seems like your tank is not finished cycling.
fish are much more hardier though you should drip aclimate all inverts/corals/(and even fish). you did fine for the clownfish, but any change would have been much easier if it had been dripped over an hour.
you mentioned white film on the clown, it could be excessive mucus. but it could also be Brook (not sure on whole name, but i think its also known as clownfish disease). though im not a vet and would ask someone with more experience. your clownfish should be swimming around at the least and if its just laying on the bottom, something is likly wrong.
Edit: i just noticed someone else mentioned brook and that the tank is still going through the cycle. a formaline dip might fix brook (double check though) and make sure you understand the procedure well because formaline can be lethal if used wrong.