Wait to add new fish until everyone in the tank has been disease free for it least 4 weeks. If your clown is not 100%, the clock has not started yet. If you add fish now, they may get ich that is still living in your tank and you won't break the cycle.
This is why a quarantine/hospital tank is essential. Keeps the ich life cycle out of your display tank and if it does break out, you can remove the fish and the ich parasites will die out in 4 weeks.
Maroons are agressive toward pretty much any fish that comes into it's territory (especially the females). They have even been known to attack keepers arms when they are cleaning the tank! If you have a larger tank (55gal+), you should be alright with other fish as long as they don't look like clowns. Tangs, gobys, blennys, sharks, whales, dolphins, giant squids...etc. :hilarious