Honey Gourami Help!

[Patpatthepat]

Hello! I have a sick female honey gourami that I am concerned about. Yesterday I noticed that she was lethargic and hovered in one place, near the surface (there is enough space at the top for her to breath from). When I went to feed the tank, she did not react which is very out of character. She seemed to have a milky left eye that I did not notice before. Admittedly I was not at home the day before yesterday, so symptoms could have started then. When I disturbed her, she would swim but otherwise she just hovered. This morning I discovered her laying on her side on the bottom of the tank. I am very concerned. She is breathing a little fast. Her mate is unaffected and behaves normally. I have no noticed any bullying between the two. If anything, the female is more food aggressive than the male. I have attached images for reference. Here is some background information on her care:

Pictures of the fish: 
https://imgur.com/a/hlNEVvb

https://imgur.com/a/3F9jT36

Tank
What is the water volume of the tank?
10 gallons
How long has the tank been running?
A year and three months
Does it have a filter?
Yes, Aquaclear 50
Does it have a heater?
Yes, Eheimjager 50 watt
What is the water temperature?
81F (Fluctuation of about a degree)
What is the entire stocking of this tank? (Please list all fish and inverts.)
M/F Honey Gourami pair, six Amano shrimp, various Cherry shrimp, bladder snails

Maintenance
How often do you change the water?
Once every week and a half
How much of the water do you change?
Varies between 25-30%
What do you use to treat your water?
Seachem prime
Do you vacuum the substrate or just the water?
Substrate

*Parameters - Very Important
Did you cycle your tank before adding fish?
Yes
What do you use to test the water?
API Freshwater Master Test 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: 7.3

Feeding
How often do you feed your fish?
Once a day
How much do you feed your fish?
1/8-1/4 of a cube of frozen food
What brand of food do you feed your fish?
Hikari
Do you feed frozen or freeze-dried foods?
Frozen mysis and bloodworms

Illness & Symptoms
How long have you had this fish?
Five months
How long ago did you first notice these symptoms?
Yesterday
In a few words, can you explain the symptoms?
Lethargic, not eating, floating in one place/lying on the ground, milky eye (?)
Have you started any treatment for the illness?
No, tried feeding live brine but no interest
Was your fish physically ill or injured upon purchase?
No
How has its behavior and appearance changed, if at all?
Lethargic, now laying at the bottom, seems fatter but no raised scales, not eating


 

[Colu]

Can get pictures up

[Mmiller2001]

Water change and observe. If it doesn't look like it's going to improve, start an antibiotic.