Skin texture difference on Erectus

[Stormhaven]

Hi Guys
Tanks been fully cycled.
Water conditions are suitable .
Nothing with any stinging potential.
Temps 74 and stable .
Thing is after noticing algae growing on there body's I noticed which may turn out to be my imagination the skin on two of my pony's looks different in a couple of areas .
Activity level is the same .
No breathing irregularities.
Feeding 3 times a day PI Mysis with additional Selcon a few times a week.
Any thoughts.
Thanks

 

[Midrats]

That's what she said.

 

[Stormhaven]

That's what she said.

I tried to make the post title as clickbait as possible I see it worked

 

[Midrats]

I was unable to resist.