Red spot on goldfish

Question
Hi. 2 days ago I noticed a small red spot on my comet goldfish.  It looks almost as if he has lost 1 of his scales.  There was something white in the center of the spot, but its gone now.  Otherwise, the fish seems healthy & his activity and eating haven't changed.  He is in a 20 gallon aquarium with 5 smaller goldfish & a snail. Thanks for any help you can give.  

Answer
Hi Donna,
First of all i must say you are extremely overstocked.
A goldfish needs 10 gallons of water each and you have 6 in total in a 20gallon. Goldfish are very messy fish and produce lots of waste thats why they need this amount of space. If he has lost one of his scales, this is probably due to scratching against sharp decor in the tank. Try and remove anything sharp in the tank because it seems like it caused him an infection.
Good luck!

Chloe.