Selcon and Zoe are excellent vitamin additives for soaking the food, very beneficial and is recommended to use at least one of them weekly as regular part of feeding. It will help keep the immune system at peak performance.
The Melafix is a natural treatment containing "teatree" oil and is completely reef safe. It is mainly for the use with skin abrasions, fin problems and in some cases mild fungal problems.
Be very careful with the other fish in the tank. Once the dominant clown is removed, they can/will change their behavior quite quickly. In all honesty, you really should consider setting up a >>Q-tank
<< and isolating the clown until it is well enough to be placed back with the others.