Is this Harlequin Rasbora eye problem contagious?

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I would like others opinions on a problem I had with my Harlequin Rasbora. He was one of the last three members of a school I had. They are all around 7 yrs old. Six days ago, I came home to see him completely missing an eye, with the other having a small white spot on the pupil. He was also paler than normal, I assumed because of the pain. I watched him over the last few days and he did not eat since, but he did appear to be able to see out of the other eye. That changed today and I decided to euthanize him. He was swimming into the plants and driftwood. I thought it was an injury caused by another fish even though I have never seen any aggression like that, but I wanted other opinions. It may be my overactive imagination, but now I'm thinking one of the Diamond Tetras eyes are looking less colorful. It was too quick to catch a picture. I looked up eye diseases and this doesn't seem to fit, but I don't want anything to happen to my other fish.
Tank
What is the water volume of the tank? 55 g
How long has the tank been running? 10 yrs
Does it have a filter? 75 g aquaclear
Does it have a heater? yes
What is the water temperature? 76.4 F
What is the entire stocking of this tank? 1 Rainbow Cichlid, 2 Harlequin Rasbora (after this one died), 10 adult Diamond Tetras, 3 baby Diamond Tetras, 1 Blue-eyed Lemon Bristlenose

Maintenance
How often do you change the water? Every 1-2 weeks
How much of the water do you change? 50%
What do you use to treat your water? Seachem Prime and APE Stresszyme
Do you vacuum the substrate or just the water? Heavily planted, so mostly just water. Substrate where I can.

*Parameters - Very Important
Did you cycle your tank before adding fish? yes
What do you use to test the water? API master kit
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate: 0 ppm
pH: 8.4

Feeding
How often do you feed your fish? twice a day
How much do you feed your fish? what they can eat in 2-3 minutes
What brand of food do you feed your fish? a variety of Bug Bites
Do you feed frozen? rarely
Do you feed freeze-dried foods? no

Illness & Symptoms
How long have you had this fish? 7 yrs
How long ago did you first notice these symptoms? 6 days ago
In a few words, can you explain the symptoms? Came home and my fish's eye was completely gone. The other one looked like it had a small white spot on the pupil.
Have you started any treatment for the illness? no
Was your fish physically ill or injured upon purchase? no
How has its behavior and appearance changed, if at all? It was also pale. I thought it may have been from the pain.

Explain your emergency situation in detail.
(Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)

Include pictures
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The ph is high, but it is high coming out of the tap. The last pic is of my tap water. Thanks for any help.

 

The overall condition of the fish isn't good. Could be old age for sure.
Cause of the poor condition it gets difficulty to fight any infections.
So contagious ??? Could be but there is a bigger chance it isn't.

 

Should be not contagious. The fish was old, the immune system broke down, opportunistic bacteria (they will always be there but only affect weakened fish) took the chance.

 

Thank you DoublDutch and MacZ for your response. He was his usual very vibrant orange bronze color before this happened and looked in the peak of health. He deteriorated to this condition in 6 days. Could pain and lack of eating cause that to happen so quickly?

 

Could pain and lack of eating cause that to happen so quickly?

When such old fish get an infection the whole system breaks down. So it's not that one thing causes the other, it's just a quick deterioration of the whole organism.