Question
Hi , we got 7 gold fishes 1 week ago. The aquarium was fixed by professionals. On the 6th day 1 small fish died.Today (7th day) I find another fish with damaged tail, seems to have broken and white at the ends.That fish is not eating too well, not moving much and currently resting(I guess) in between the plants.The other fishes look ok but are eating less then the first few days.

Answer
How big is your setup?  How big are the fish?  What kind of filtration and aeration is there?  Have you tested the pH, hardness, ammonia, and nitrite?  The tail damage could be from the other fish, from the filter intake, or from an infection such as fin and tail rot.  Either way, the addition of aquarium salt at a tablespoon per 5 gallons and MelaFix by Aquarium Pharmaceuticals should help heal the area.  I suggest reading over my web site for information about aquariums in general, goldfish, etc.  Here are some pages to check out.

http://www.fishpondinfo.com/fish.htm
http://www.fishpondinfo.com/chem.htm
http://www.fishpondinfo.com/gfish.htm
http://www.fishpondinfo.com/fishcare/treat.htm

Good luck!