Clowns are agressive towards each other for dominance by nature so it depends on your luck if they are overly agressive till there is is fatality. IMO you should try to introduce a bunch of them into the tank at the same time and choose the clowns which are of the same size.
I had 4 clowns living in my 3 1.5 2 tank with one anemone without problem - just that the dominant clown will hog the anemone in the day but all the clowns will hide in the anemone in the night together.
IN that case, IMO I think you can remove all your SPS and LPS and stir up the tank before sucking up the "dirt" and do 20% WC. Let the tank settle before putting back your SPS and LPS.