Ugh. Clowns likely have ich because you have them in a 5g tank - way too small for them and stressing them out, causing lowered immune response and inability to fight off ich. Moving them to the 30 will help reduce stress, but may or may not help with the ich (it won't cure them, but will help with stress which could overtime improve their immune system - but that might not be in time for them to fight off this bought of ich - and it certainly won't cure it, it will just move ich to your 30g tank). If you want to cure ich, read up on the stickies in the fish disease forum.
As for the nem, sounds like a condy, which clowns don't host and which may eat clowns. Could also be a sebae. Most importantly, they are hard to take care of, no guarantee your clowns will host it, need incredibly strong lighting, and stable and clean water parameters. Most recommend against trying to keep a nem in a tank that has been set up for less than a year. I'd return the nem to the store.
