Is This A Disease?

I brought home 3 endlers on Monday, and one seemed slightly less vibrant than the others. His black spot was more dark silver. Now, the others spots are slightly darker. It's not fuzzy, and it is kinda metalic.
Info:
10 gallon tank
75 degrees
3 endlers and a mystery snail
Cycled tank
Is something wrong?

 

Can you post some pictures?

 

I can try, they won't hold still.

So sorry for the bad quality pics, this tank doesn’t have lights.

They are swimming and eating normally, but instead of this black color it is more silver.

 

He's a cobra? That just looks like his pattern to me. I have some and their patterns are all different from one another.

 

I have no idea, lol there were lucky finds from petsmart. Each was only 4 dollars

 

Yeah those are the same ones I got. Just the color pattern IMO.