Matt were the fish gasping at the top? If so it is a lack of oxygen.
Once you check to see that the tank has not cycled, you can start again.
This time;
Wait for one month until you add another fish to your tank.
Add only add one fish per month to your tank as adding too many at the same time affects the balance in a small tank like yours.
It is a good idea to ask here about fish suitable to your tank or go to
www.wetwebmedia.com
Never add a tang to 25 gallon tank. If the LFS that sold you the tang knew it was going in a 25 gallon change LFS.
I don't mean to lecture. I know the loss is tough on you.