Hi, this is my first saltwater aquarium. It has been running with fish in it for a week now. The shop we purchased everything from sold us a "preran" "presetup" tank saying we wouldn't have to wait a month for everything to settle in. We had originally placed in 2 clownfish. On the third day, we noticed one of the clowns was seemingly "gasping" and otherwise having a hard time breathing. We called the shop and they said he must have induced issues in transit so they would replace him and we shouldn't need to worry about the other clown. Now with this new replacement clown on day 5, we are noticing that he is keeping his mouth open and his lips seem to be getting more pale. What would cause this? Is there a treatment we can give him to help? Do I have to worry about our other clown catching it?