Scales changing colors
 

Can anyone help? Our goldfish is changing and I am not sure what is wrong? I noticed a darker scale a month or so ago. Did not think much about as our fish have changed from gold to white/silver or the opposite. Now she has 4 darker "scales" and they are protruding and soft. Thanks in advance.
I will mention I know we have too many fish in the tank but when we got it a year ago it was a good size. They just grew faster than expected!