wow... slow down...
Tank got water 10 days ago. Rock was dry, so you got NO bacterial filtration at the moment. Yet you already added 6 fish in there. Just wait. Like another month before adding anything else.
And a 50% water change is a bit extreme. You need to ensure that the water is the same temperature, salinity and PH. Else you will kill your fish when you suddenly change all those parameters too quickly. Alternative would be to slowly add the new water, like in a tap that is almost closed, not dripping but yet not running. Should take you an hour to refill. It is exactly like acclimatizing your fish, but instead of the fish in bags and you add a bit of water slowly, they are now in a much bigger bag (tank) and you are adding water slowly.
And wait with the corals. another month to 6 weeks. Let your tank stabilize first over the next couple of weeks. Slight overfeeding, too many new fish, no filtration yet, and you are in for a bumpy ride for the next few weeks.
Just take it slow.