Ryu's time is coming :(

First off everyone, thank you for viewing, and I wont post that long descriptive list of everything because I already feel whats gonna happen, and its so sad, but I have to accept it. That doesnt mean I will give up. He is also way duller than usually, he is usually very striking and vibrant. I have had Ryu about a year now, in which he was 3 months old when I got him. Here he is a year later, suffering from what I believe is early dropsy or some kinda organ failure. I know little about dropsy besides what I read online and from my betta books. I noticed his scales looked weird a few week ago and i have kept up the water changes a few extra times. I use Prime water conditioner, I hope thats a good safe brand. His heater and filter have lately been all scummy, no matter how much I clean them or scrub his substrate with hot jet water during a full water change. He eats all his food too, theres nothing left behind. In case anyone is wondering, its a 2.5 gal tank-I do a half a change a week and then a full the next week, but since this scum stuff appeared, I have had to do a full a week. Its not algae or anything, no live plants and little sun. I think his new sand substrate is made out of limestone, as my Ph levels are still acidic even after a day of a full water change, which would explain why Ryu's fins are kinda melted looking at the ends. So I took that out and the ph levels have stayed down. It was a some petsmart aquarium white sand substrate. When his scales started looking weird, I have been adding a tsp of epsom salt to his water after each full water change- i read online that it helps with dropsy and eye problems. This morning at 8:34am he was struggling eating his pellets and swimming strange, resembling a swim bladder problem. I took him out an quarantined him in a cup for now with a pinch of epsom salt, I am scared to add in anything else. If he doesnt make it, thats ok it just must be his time just like when I lost Sakura and Natsuko from unknown reasons. He's my good fiesty boy with the dorky big pectoral fins and I thank him for being a part of my life. When he passes, he will still live on. He will be burried right next to his sisters. The hilarious thing is, Izume is still alive and doing well. He is still red and recovering from septicemia well, his fins have grown back and he is less bloody. He is super active and is acting liek he isnt sick! Lol. That fish is a tank- no pun intended!

Here are some pics of Ryu: