I hatched an animal like that a few years back (2012), it almost appeared as a thick eye cap which would peal off and go away and come right back.
This animal was the only one in the clutch with the issue.
The female had never produce any animal with that type of issue (either before or after), as for the male it was here on a loan, not sure if it was used in further breeding.
I kept 2 of the siblings which were perfect and have since produces perfect offsprings.
I do not believe this to be genetic. Just a diffect.
Sent from my SM-G900V using Tapatalk