OK - so if you look at my signature - you will see a link.
HOW TO ASK FOR DISEASE DIAGNOSIS HELP LINK
Click the link - it will give you the information that is helpful before posting a question - it's also at the top of the reef disease forum (you're in the general discussion area). Up front - I will say 2 things:
1. There is no such thing as a 2 week quarantine - so your fish have not been quarantined.
2. It is possible for you to introduce disease into a tank with coral (though more uncommon).
3. In the future if you use the hashtag
#fishmedic - it will bring a number of people to your post that can help you.
To answer your questions - the white stuff on the rocks is not related to the white stuff on your clowns. There is a quarantine protocol at the top of the fish disease forum involving a month of copper followed by praziquantel for a couple doses - followed by 2 weeks observation.
Normally it's more common for clowns to have brooklynella - however this does not affect other fish in the same manner - so it sounds like you have 'velvet' in your tank. Since there are no pictures of your fish - I would consider treating the remainder of the fish (if any) in a hospital tank with copper as discussed above - followed by prazipro.
PS - Jay Hemdal - another of the 'fish medics' also posted the link with the questions that if answered, would help us help you.