Please help diagnose my betta...I think he might have multiple diseases

To start off, there are no problems with water quality. I have experience with fish and the nitrogen cycle and have tested parameters every day and found no problems. This particular betta has been living alone in a 5-gallon cycled tank for almost a year now. This is the first time I have had a sick fish.

My betta is experiencing the following symptoms:
1.) fins have rapidly deteriorated (within a week, his fins are less than half their original size)
2.) color loss (was a vibrant blue, but now turning pale and grayish)
3.) rapid weight loss except in area of pectoral fins, which has maintained its original size
4.) eyes bulging out -- Fish is unable to see well enough to eat food. He will try pouncing on the food but completely miss by a half inch.
5.) lethargy -- he hardly moves at all when before he was a very active fish

I have tried treating with medications: first with kanaplex, then with API fungus cure. He looked a little better after the first dose of kanaplex, but then got worse again. I did not see any change in his condition with the API fungus cure.

Any ideas on what this could be and/or what I can do to treat him?

A picture can tell a thousand words, please post a few of his fins, eyes, body condition etc.

What is the water change schedule like?
When he poops, what does it look like?
What is the temp of the tank?

A good way to get a betta to eat is by taking a blood worm (the frozen kind) and hold it with tweezers right in front of their face.

pop eye, fin rot. i all i know is that good clean filtered water is best. btw do you condition your water before refilling after water change?

I have attached a picture. He is looking a lot worse today since I got home from work. He hangs out at the bottom of the tank, and it looks like he's struggling to breathe. To answer the questions, I change the water 2 times per week (25% each). The poop looks like tiny brown dots. The tank is at 77 degrees.

Unfortunately, the fish didn't end up making it. I am now working on cycling a new tank so I can get a new fish in a few weeks.