endler has a black eye

[Canoe]

I just came back from 5 days away, and found that one of my male Endlers developed a black eye while I was gone. That is, he used to have black pupils and gold irises, and now one one of his eyes, both pupil and iris are black. He also developed some additional black bars of coloration on his body -- though new, these seem normal to me.

What happened? Is he just growing and changing? Or is he sick? He seems to be behaving normally. I've had him for about 2 weeks.

Here are the specs:
7g bowfront with Whisper 5-15 filter
3 tiny julii cory cats
1 sparkling gourami
2 male Endler's livebearers

Ammonia, Nitrite 0
Nitrate 20

Tank established for about 1 month. 30% water changes with Amquel twice weekly.

Temp, unfortunately, has varied between 78 and 84+ degrees -- I did not leave the A/C on while away, so I'm sure it was plenty toasty here. Also, I did not feed during the five days away.

Any clues?

[Kasakato]

Wow. This is hard. How are its scales? Are they normal? Can you get a pic of possible? Is that anything what it looks like: http://www.aquaworldaquarium.com/Endler's_Livebearer.html

[Boohoo]

I have a calico fantail that had his eye change the same as your fish. It happened about 3-4 months ago and he is just fine.

[Canoe]

Everything looks normal scale-wise. I will try to get a pic, but man he's so tiny, I hope it will come out!